* [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB
@ 2025-08-13 13:46 Alexandre Derumier via pve-devel
2025-08-13 14:25 ` Fabian Grünbichler
0 siblings, 1 reply; 4+ messages in thread
From: Alexandre Derumier via pve-devel @ 2025-08-13 13:46 UTC (permalink / raw)
To: pve-devel; +Cc: Alexandre Derumier
[-- Attachment #1: Type: message/rfc822, Size: 56937 bytes --]
From: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
To: pve-devel@lists.proxmox.com
Subject: [PATCH qemu-server] qcow2: increase cache-size to 1GB
Date: Wed, 13 Aug 2025 15:46:33 +0200
Message-ID: <20250813134633.541556-1-alexandre.derumier@groupe-cyllene.com>
Currently, the qcow2 maximum cache-size is 32MB, enough to handle metadatas
for a 256GB images with 65k cluster size.
if cache-size is not big enough, performance are really bad
This patch increase cache to 1GB, enough to handle 8TB image
with default 32MB cache
fio benchmark 4k randread/write:
256GB image : 32MB cache : 40000 iops
1TB image: 32MB cache: 2500 iops
8TB image: 32MB cache: 2500 iops
1TB image: 1G cache: 40000 iops
8TB image: 1G cache: 40000 iops
the cache-size value is a maximum value, memory is not reserved at vm start.
Also, the metadatas not used are removed from the cache after 10min by default.
https://gitlab.com/qemu-project/qemu/-/blob/master/docs/qcow2-cache.txt
Signed-off-by: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
---
src/PVE/QemuServer/Blockdev.pm | 3 +++
src/test/cfg2cmd/bootorder-empty.conf.cmd | 6 +++---
src/test/cfg2cmd/bootorder-legacy.conf.cmd | 6 +++---
src/test/cfg2cmd/bootorder.conf.cmd | 6 +++---
.../cfg2cmd/cputype-icelake-client-deprecation.conf.cmd | 2 +-
src/test/cfg2cmd/ide.conf.cmd | 2 +-
src/test/cfg2cmd/q35-ide.conf.cmd | 2 +-
src/test/cfg2cmd/q35-linux-hostpci-mapping.conf.cmd | 2 +-
src/test/cfg2cmd/q35-linux-hostpci-multifunction.conf.cmd | 2 +-
src/test/cfg2cmd/q35-linux-hostpci-template.conf.cmd | 2 +-
src/test/cfg2cmd/q35-linux-hostpci-x-pci-overrides.conf.cmd | 2 +-
src/test/cfg2cmd/q35-linux-hostpci.conf.cmd | 2 +-
src/test/cfg2cmd/q35-simple.conf.cmd | 2 +-
src/test/cfg2cmd/seabios_serial.conf.cmd | 2 +-
src/test/cfg2cmd/simple-backingchain.conf.cmd | 4 ++--
src/test/cfg2cmd/simple-virtio-blk.conf.cmd | 2 +-
src/test/cfg2cmd/simple1-template.conf.cmd | 4 ++--
src/test/cfg2cmd/simple1.conf.cmd | 2 +-
src/test/run_qemu_img_convert_tests.pl | 6 +++---
19 files changed, 31 insertions(+), 28 deletions(-)
diff --git a/src/PVE/QemuServer/Blockdev.pm b/src/PVE/QemuServer/Blockdev.pm
index f5798cbf..895f1a6a 100644
--- a/src/PVE/QemuServer/Blockdev.pm
+++ b/src/PVE/QemuServer/Blockdev.pm
@@ -381,6 +381,9 @@ my sub generate_format_blockdev {
$blockdev->{'discard-no-unref'} = JSON::true if $format eq 'qcow2';
}
+ #increase qcow2 maximum cache size to 1GB memory, enough to handle 8TB disk image with 64k clusters.
+ $blockdev->{'cache-size'} = 1073741824 if $format eq 'qcow2';
+
return $blockdev;
}
diff --git a/src/test/cfg2cmd/bootorder-empty.conf.cmd b/src/test/cfg2cmd/bootorder-empty.conf.cmd
index 3516b344..5e16bd44 100644
--- a/src/test/cfg2cmd/bootorder-empty.conf.cmd
+++ b/src/test/cfg2cmd/bootorder-empty.conf.cmd
@@ -32,11 +32,11 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2' \
-device 'lsi,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"e6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"f6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"drive-scsi4","read-only":false,"throttle-group":"throttle-drive-scsi4"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"e6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"f6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"drive-scsi4","read-only":false,"throttle-group":"throttle-drive-scsi4"}' \
-device 'scsi-hd,bus=scsihw0.0,scsi-id=4,drive=drive-scsi4,id=scsi4,device_id=drive-scsi4,write-cache=on' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
-device 'virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,iothread=iothread-virtio0,write-cache=on' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"eeb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"feb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"drive-virtio1","read-only":false,"throttle-group":"throttle-drive-virtio1"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"eeb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"feb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"drive-virtio1","read-only":false,"throttle-group":"throttle-drive-virtio1"}' \
-device 'virtio-blk-pci,drive=drive-virtio1,id=virtio1,bus=pci.0,addr=0xb,iothread=iothread-virtio1,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=A2:C0:43:77:08:A0,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256' \
diff --git a/src/test/cfg2cmd/bootorder-legacy.conf.cmd b/src/test/cfg2cmd/bootorder-legacy.conf.cmd
index c86ab6f9..ca476f19 100644
--- a/src/test/cfg2cmd/bootorder-legacy.conf.cmd
+++ b/src/test/cfg2cmd/bootorder-legacy.conf.cmd
@@ -32,11 +32,11 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=200' \
-device 'lsi,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"e6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"f6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"drive-scsi4","read-only":false,"throttle-group":"throttle-drive-scsi4"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"e6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"f6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"drive-scsi4","read-only":false,"throttle-group":"throttle-drive-scsi4"}' \
-device 'scsi-hd,bus=scsihw0.0,scsi-id=4,drive=drive-scsi4,id=scsi4,device_id=drive-scsi4,write-cache=on' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
-device 'virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,iothread=iothread-virtio0,write-cache=on' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"eeb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"feb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"drive-virtio1","read-only":false,"throttle-group":"throttle-drive-virtio1"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"eeb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"feb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"drive-virtio1","read-only":false,"throttle-group":"throttle-drive-virtio1"}' \
-device 'virtio-blk-pci,drive=drive-virtio1,id=virtio1,bus=pci.0,addr=0xb,iothread=iothread-virtio1,bootindex=302,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=A2:C0:43:77:08:A0,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=100' \
diff --git a/src/test/cfg2cmd/bootorder.conf.cmd b/src/test/cfg2cmd/bootorder.conf.cmd
index 48f9da8b..44294f0c 100644
--- a/src/test/cfg2cmd/bootorder.conf.cmd
+++ b/src/test/cfg2cmd/bootorder.conf.cmd
@@ -32,11 +32,11 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=103' \
-device 'lsi,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"e6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"f6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"drive-scsi4","read-only":false,"throttle-group":"throttle-drive-scsi4"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"e6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"f6bf62e20f6c14a2c19bd6f1f5ac36c","read-only":false},"node-name":"drive-scsi4","read-only":false,"throttle-group":"throttle-drive-scsi4"}' \
-device 'scsi-hd,bus=scsihw0.0,scsi-id=4,drive=drive-scsi4,id=scsi4,device_id=drive-scsi4,bootindex=102,write-cache=on' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
-device 'virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,iothread=iothread-virtio0,write-cache=on' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"eeb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"feb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"drive-virtio1","read-only":false,"throttle-group":"throttle-drive-virtio1"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"eeb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"feb683fb9c516c1a8707c917f0d7a38","read-only":false},"node-name":"drive-virtio1","read-only":false,"throttle-group":"throttle-drive-virtio1"}' \
-device 'virtio-blk-pci,drive=drive-virtio1,id=virtio1,bus=pci.0,addr=0xb,iothread=iothread-virtio1,bootindex=100,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=A2:C0:43:77:08:A0,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=101' \
diff --git a/src/test/cfg2cmd/cputype-icelake-client-deprecation.conf.cmd b/src/test/cfg2cmd/cputype-icelake-client-deprecation.conf.cmd
index e6429c9f..5ae89e2e 100644
--- a/src/test/cfg2cmd/cputype-icelake-client-deprecation.conf.cmd
+++ b/src/test/cfg2cmd/cputype-icelake-client-deprecation.conf.cmd
@@ -28,6 +28,6 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=200' \
-device 'virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/base-8006-disk-0.qcow2","node-name":"e417d5947e69c5890b1e3ddf8a68167","read-only":false},"node-name":"f417d5947e69c5890b1e3ddf8a68167","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/base-8006-disk-0.qcow2","node-name":"e417d5947e69c5890b1e3ddf8a68167","read-only":false},"node-name":"f417d5947e69c5890b1e3ddf8a68167","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
-device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,bootindex=100,write-cache=on' \
-machine 'type=pc+pve0'
diff --git a/src/test/cfg2cmd/ide.conf.cmd b/src/test/cfg2cmd/ide.conf.cmd
index 6b5a52a9..bbdcc70b 100644
--- a/src/test/cfg2cmd/ide.conf.cmd
+++ b/src/test/cfg2cmd/ide.conf.cmd
@@ -39,7 +39,7 @@
-blockdev '{"driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"driver":"raw","file":{"aio":"threads","cache":{"direct":false,"no-flush":false},"driver":"file","filename":"/mnt/pve/cifs-store/template/iso/three.iso","node-name":"e35557bae4bcbf9edc9f7ff7f132f30","read-only":true},"node-name":"f35557bae4bcbf9edc9f7ff7f132f30","read-only":true},"node-name":"drive-ide3","read-only":true,"throttle-group":"throttle-drive-ide3"}' \
-device 'ide-cd,bus=ide.1,unit=1,drive=drive-ide3,id=ide3,bootindex=203' \
-device 'virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-2.qcow2","node-name":"ec11e0572184321efc5835152b95d5d","read-only":false},"node-name":"fc11e0572184321efc5835152b95d5d","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-2.qcow2","node-name":"ec11e0572184321efc5835152b95d5d","read-only":false},"node-name":"fc11e0572184321efc5835152b95d5d","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}'
-device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,bootindex=100,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=2E:01:68:F9:9C:87,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=300' \
diff --git a/src/test/cfg2cmd/q35-ide.conf.cmd b/src/test/cfg2cmd/q35-ide.conf.cmd
index 475e58d9..dd8b8590 100644
--- a/src/test/cfg2cmd/q35-ide.conf.cmd
+++ b/src/test/cfg2cmd/q35-ide.conf.cmd
@@ -38,7 +38,7 @@
-blockdev '{"driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"driver":"raw","file":{"aio":"threads","cache":{"direct":false,"no-flush":false},"driver":"file","filename":"/mnt/pve/cifs-store/template/iso/three.iso","node-name":"e35557bae4bcbf9edc9f7ff7f132f30","read-only":true},"node-name":"f35557bae4bcbf9edc9f7ff7f132f30","read-only":true},"node-name":"drive-ide3","read-only":true,"throttle-group":"throttle-drive-ide3"}' \
-device 'ide-cd,bus=ide.3,unit=0,drive=drive-ide3,id=ide3,bootindex=203' \
-device 'virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-2.qcow2","node-name":"ec11e0572184321efc5835152b95d5d","read-only":false},"node-name":"fc11e0572184321efc5835152b95d5d","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-2.qcow2","node-name":"ec11e0572184321efc5835152b95d5d","read-only":false},"node-name":"fc11e0572184321efc5835152b95d5d","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
-device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,bootindex=100,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=2E:01:68:F9:9C:87,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=300' \
diff --git a/src/test/cfg2cmd/q35-linux-hostpci-mapping.conf.cmd b/src/test/cfg2cmd/q35-linux-hostpci-mapping.conf.cmd
index b0c3e587..2b6d83ae 100644
--- a/src/test/cfg2cmd/q35-linux-hostpci-mapping.conf.cmd
+++ b/src/test/cfg2cmd/q35-linux-hostpci-mapping.conf.cmd
@@ -11,7 +11,7 @@
-smbios 'type=1,uuid=3dd750ce-d910-44d0-9493-525c0be4e687' \
-object '{"id":"throttle-drive-efidisk0","limits":{},"qom-type":"throttle-group"}' \
-blockdev '{"driver":"raw","file":{"driver":"file","filename":"/usr/share/pve-edk2-firmware//OVMF_CODE.fd"},"node-name":"pflash0","read-only":true}' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
-global 'ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off' \
-smp '2,sockets=2,cores=1,maxcpus=2' \
-nodefaults \
diff --git a/src/test/cfg2cmd/q35-linux-hostpci-multifunction.conf.cmd b/src/test/cfg2cmd/q35-linux-hostpci-multifunction.conf.cmd
index b4aa46f5..1c7ad6a9 100644
--- a/src/test/cfg2cmd/q35-linux-hostpci-multifunction.conf.cmd
+++ b/src/test/cfg2cmd/q35-linux-hostpci-multifunction.conf.cmd
@@ -11,7 +11,7 @@
-smbios 'type=1,uuid=3dd750ce-d910-44d0-9493-525c0be4e687' \
-object '{"id":"throttle-drive-efidisk0","limits":{},"qom-type":"throttle-group"}' \
-blockdev '{"driver":"raw","file":{"driver":"file","filename":"/usr/share/pve-edk2-firmware//OVMF_CODE.fd"},"node-name":"pflash0","read-only":true}' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
-global 'ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off' \
-smp '2,sockets=2,cores=1,maxcpus=2' \
-nodefaults \
diff --git a/src/test/cfg2cmd/q35-linux-hostpci-template.conf.cmd b/src/test/cfg2cmd/q35-linux-hostpci-template.conf.cmd
index 20e3c81d..14290017 100644
--- a/src/test/cfg2cmd/q35-linux-hostpci-template.conf.cmd
+++ b/src/test/cfg2cmd/q35-linux-hostpci-template.conf.cmd
@@ -10,7 +10,7 @@
-daemonize \
-object '{"id":"throttle-drive-efidisk0","limits":{},"qom-type":"throttle-group"}' \
-blockdev '{"driver":"raw","file":{"driver":"file","filename":"/usr/share/pve-edk2-firmware//OVMF_CODE.fd"},"node-name":"pflash0","read-only":true}' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/base-100-disk-1.qcow2","node-name":"eb6bec0e3c391fabb7fb7dd73ced9bf","read-only":true},"node-name":"fb6bec0e3c391fabb7fb7dd73ced9bf","read-only":true},"node-name":"drive-efidisk0","read-only":true,"throttle-group":"throttle-drive-efidisk0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/base-100-disk-1.qcow2","node-name":"eb6bec0e3c391fabb7fb7dd73ced9bf","read-only":true},"node-name":"fb6bec0e3c391fabb7fb7dd73ced9bf","read-only":true},"node-name":"drive-efidisk0","read-only":true,"throttle-group":"throttle-drive-efidisk0"}' \
-smp '1,sockets=1,cores=1,maxcpus=1' \
-nodefaults \
-boot 'menu=on,strict=on,reboot-timeout=1000,splash=/usr/share/qemu-server/bootsplash.jpg' \
diff --git a/src/test/cfg2cmd/q35-linux-hostpci-x-pci-overrides.conf.cmd b/src/test/cfg2cmd/q35-linux-hostpci-x-pci-overrides.conf.cmd
index 6c4937c7..ff2f4db9 100644
--- a/src/test/cfg2cmd/q35-linux-hostpci-x-pci-overrides.conf.cmd
+++ b/src/test/cfg2cmd/q35-linux-hostpci-x-pci-overrides.conf.cmd
@@ -11,7 +11,7 @@
-smbios 'type=1,uuid=3dd750ce-d910-44d0-9493-525c0be4e687' \
-object '{"id":"throttle-drive-efidisk0","limits":{},"qom-type":"throttle-group"}' \
-blockdev '{"driver":"raw","file":{"driver":"file","filename":"/usr/share/pve-edk2-firmware//OVMF_CODE.fd"},"node-name":"pflash0","read-only":true}' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
-global 'ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off' \
-smp '2,sockets=2,cores=1,maxcpus=2' \
-nodefaults \
diff --git a/src/test/cfg2cmd/q35-linux-hostpci.conf.cmd b/src/test/cfg2cmd/q35-linux-hostpci.conf.cmd
index 19e6ba3c..c2c68c3a 100644
--- a/src/test/cfg2cmd/q35-linux-hostpci.conf.cmd
+++ b/src/test/cfg2cmd/q35-linux-hostpci.conf.cmd
@@ -11,7 +11,7 @@
-smbios 'type=1,uuid=3dd750ce-d910-44d0-9493-525c0be4e687' \
-object '{"id":"throttle-drive-efidisk0","limits":{},"qom-type":"throttle-group"}' \
-blockdev '{"driver":"raw","file":{"driver":"file","filename":"/usr/share/pve-edk2-firmware//OVMF_CODE.fd"},"node-name":"pflash0","read-only":true}' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
-global 'ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off' \
-smp '2,sockets=2,cores=1,maxcpus=2' \
-nodefaults \
diff --git a/src/test/cfg2cmd/q35-simple.conf.cmd b/src/test/cfg2cmd/q35-simple.conf.cmd
index e3f712c3..939eb96f 100644
--- a/src/test/cfg2cmd/q35-simple.conf.cmd
+++ b/src/test/cfg2cmd/q35-simple.conf.cmd
@@ -11,7 +11,7 @@
-smbios 'type=1,uuid=3dd750ce-d910-44d0-9493-525c0be4e687' \
-object '{"id":"throttle-drive-efidisk0","limits":{},"qom-type":"throttle-group"}' \
-blockdev '{"driver":"raw","file":{"driver":"file","filename":"/usr/share/pve-edk2-firmware//OVMF_CODE.fd"},"node-name":"pflash0","read-only":true}' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"cache":{"direct":false,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":false,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vz/images/100/vm-100-disk-1.qcow2","node-name":"e70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"f70e3017c5a79fdee5a04aa92ac1e9c","read-only":false},"node-name":"drive-efidisk0","read-only":false,"throttle-group":"throttle-drive-efidisk0"}'
-global 'ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off' \
-smp '2,sockets=1,cores=2,maxcpus=2' \
-nodefaults \
diff --git a/src/test/cfg2cmd/seabios_serial.conf.cmd b/src/test/cfg2cmd/seabios_serial.conf.cmd
index 8fc0509b..eeeb7b49 100644
--- a/src/test/cfg2cmd/seabios_serial.conf.cmd
+++ b/src/test/cfg2cmd/seabios_serial.conf.cmd
@@ -28,7 +28,7 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=200' \
-device 'virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"ecd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"fcd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"ecd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"fcd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}'
-device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,bootindex=100,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=A2:C0:43:77:08:A0,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=300' \
diff --git a/src/test/cfg2cmd/simple-backingchain.conf.cmd b/src/test/cfg2cmd/simple-backingchain.conf.cmd
index 4ac24b93..504cec67 100644
--- a/src/test/cfg2cmd/simple-backingchain.conf.cmd
+++ b/src/test/cfg2cmd/simple-backingchain.conf.cmd
@@ -26,8 +26,8 @@
-device 'virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3,free-page-reporting=on' \
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'lsi,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"backing":{"backing":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","discard-no-unref":true,"driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vzsnapext/images/8006/snap1-vm-8006-disk-0.qcow2","node-name":"ea91a385a49a008a4735c0aec5c6749","read-only":false},"node-name":"fa91a385a49a008a4735c0aec5c6749","read-only":false},"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","discard-no-unref":true,"driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vzsnapext/images/8006/snap2-vm-8006-disk-0.qcow2","node-name":"ec0289317073959d450248d8cd7a480","read-only":false},"node-name":"fc0289317073959d450248d8cd7a480","read-only":false},"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","discard-no-unref":true,"driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vzsnapext/images/8006/vm-8006-disk-0.qcow2","node-name":"e74f4959037afb46eddc7313c43dfdd","read-only":false},"node-name":"f74f4959037afb46eddc7313c43dfdd","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"backing":{"backing":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","discard-no-unref":true,"driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vzsnapext/images/8006/snap1-vm-8006-disk-0.qcow2","node-name":"ea91a385a49a008a4735c0aec5c6749","read-only":false},"node-name":"fa91a385a49a008a4735c0aec5c6749","read-only":false},"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","discard-no-unref":true,"driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vzsnapext/images/8006/snap2-vm-8006-disk-0.qcow2","node-name":"ec0289317073959d450248d8cd7a480","read-only":false},"node-name":"fc0289317073959d450248d8cd7a480","read-only":false},"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","discard-no-unref":true,"driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"file","filename":"/var/lib/vzsnapext/images/8006/vm-8006-disk-0.qcow2","node-name":"e74f4959037afb46eddc7313c43dfdd","read-only":false},"node-name":"f74f4959037afb46eddc7313c43dfdd","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}'
-device 'scsi-hd,bus=scsihw0.0,scsi-id=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,write-cache=on' \
- -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"backing":{"backing":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"native","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"host_device","filename":"/dev/veegee/snap1-vm-8006-disk-0.qcow2","node-name":"e25f58d3e6e11f2065ad41253988915","read-only":false},"node-name":"f25f58d3e6e11f2065ad41253988915","read-only":false},"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"native","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"host_device","filename":"/dev/veegee/snap2-vm-8006-disk-0.qcow2","node-name":"e9415bb5e484c1e25d25063b01686fe","read-only":false},"node-name":"f9415bb5e484c1e25d25063b01686fe","read-only":false},"cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"native","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"host_device","filename":"/dev/veegee/vm-8006-disk-0.qcow2","node-name":"e87358a470ca311f94d5cc61d1eb428","read-only":false},"node-name":"f87358a470ca311f94d5cc61d1eb428","read-only":false},"node-name":"drive-scsi1","read-only":false,"throttle-group":"throttle-drive-scsi1"}' \
+ -blockdev '{"detect-zeroes":"on","discard":"ignore","driver":"throttle","file":{"backing":{"backing":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"native","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"host_device","filename":"/dev/veegee/snap1-vm-8006-disk-0.qcow2","node-name":"e25f58d3e6e11f2065ad41253988915","read-only":false},"node-name":"f25f58d3e6e11f2065ad41253988915","read-only":false},"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"native","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"host_device","filename":"/dev/veegee/snap2-vm-8006-disk-0.qcow2","node-name":"e9415bb5e484c1e25d25063b01686fe","read-only":false},"node-name":"f9415bb5e484c1e25d25063b01686fe","read-only":false},"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"on","discard":"ignore","driver":"qcow2","file":{"aio":"native","cache":{"direct":true,"no-flush":false},"detect-zeroes":"on","discard":"ignore","driver":"host_device","filename":"/dev/veegee/vm-8006-disk-0.qcow2","node-name":"e87358a470ca311f94d5cc61d1eb428","read-only":false},"node-name":"f87358a470ca311f94d5cc61d1eb428","read-only":false},"node-name":"drive-scsi1","read-only":false,"throttle-group":"throttle-drive-scsi1"}'
-device 'scsi-hd,bus=scsihw0.0,scsi-id=1,drive=drive-scsi1,id=scsi1,device_id=drive-scsi1,write-cache=on' \
-machine 'type=pc+pve0'
diff --git a/src/test/cfg2cmd/simple-virtio-blk.conf.cmd b/src/test/cfg2cmd/simple-virtio-blk.conf.cmd
index a9acb0cf..0c672c70 100644
--- a/src/test/cfg2cmd/simple-virtio-blk.conf.cmd
+++ b/src/test/cfg2cmd/simple-virtio-blk.conf.cmd
@@ -28,7 +28,7 @@
-device 'virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3,free-page-reporting=on' \
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=200' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-name":"drive-virtio0","read-only":false,"throttle-group":"throttle-drive-virtio0"}' \
-device 'virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,iothread=iothread-virtio0,bootindex=100,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=A2:C0:43:77:08:A0,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=300' \
diff --git a/src/test/cfg2cmd/simple1-template.conf.cmd b/src/test/cfg2cmd/simple1-template.conf.cmd
index 369b4de9..e57968b1 100644
--- a/src/test/cfg2cmd/simple1-template.conf.cmd
+++ b/src/test/cfg2cmd/simple1-template.conf.cmd
@@ -27,10 +27,10 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=200' \
-device 'virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/base-8006-disk-1.qcow2","node-name":"e1085774206ae4a6b6bf8426ff08f16","read-only":true},"node-name":"f1085774206ae4a6b6bf8426ff08f16","read-only":true},"node-name":"drive-scsi0","read-only":true,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/base-8006-disk-1.qcow2","node-name":"e1085774206ae4a6b6bf8426ff08f16","read-only":true},"node-name":"f1085774206ae4a6b6bf8426ff08f16","read-only":true},"node-name":"drive-scsi0","read-only":true,"throttle-group":"throttle-drive-scsi0"}' \
-device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,write-cache=on' \
-device 'ahci,id=ahci0,multifunction=on,bus=pci.0,addr=0x7' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/base-8006-disk-0.qcow2","node-name":"eab334c2e07734480f33dd80d89871b","read-only":true},"node-name":"fab334c2e07734480f33dd80d89871b","read-only":true},"node-name":"drive-sata0","read-only":true,"throttle-group":"throttle-drive-sata0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/base-8006-disk-0.qcow2","node-name":"eab334c2e07734480f33dd80d89871b","read-only":true},"node-name":"fab334c2e07734480f33dd80d89871b","read-only":true},"node-name":"drive-sata0","read-only":true,"throttle-group":"throttle-drive-sata0"}' \
-device 'ide-cd,bus=ahci0.0,drive=drive-sata0,id=sata0,write-cache=on' \
-machine 'accel=tcg,smm=off,type=pc+pve0' \
-snapshot
diff --git a/src/test/cfg2cmd/simple1.conf.cmd b/src/test/cfg2cmd/simple1.conf.cmd
index 49b848f2..16fbd098 100644
--- a/src/test/cfg2cmd/simple1.conf.cmd
+++ b/src/test/cfg2cmd/simple1.conf.cmd
@@ -28,7 +28,7 @@
-iscsi 'initiator-name=iqn.1993-08.org.debian:01:aabbccddeeff' \
-device 'ide-cd,bus=ide.1,unit=0,id=ide2,bootindex=200' \
-device 'virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5' \
- -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"ecd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"fcd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
+ -blockdev '{"detect-zeroes":"unmap","discard":"unmap","driver":"throttle","file":{"cache":{"direct":true,"no-flush":false},"cache-size":1073741824,"detect-zeroes":"unmap","discard":"unmap","driver":"qcow2","file":{"aio":"io_uring","cache":{"direct":true,"no-flush":false},"detect-zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/vz/images/8006/vm-8006-disk-0.qcow2","node-name":"ecd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"fcd04be4259153b8293415fefa2a84c","read-only":false},"node-name":"drive-scsi0","read-only":false,"throttle-group":"throttle-drive-scsi0"}' \
-device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,device_id=drive-scsi0,bootindex=100,write-cache=on' \
-netdev 'type=tap,id=net0,ifname=tap8006i0,script=/usr/libexec/qemu-server/pve-bridge,downscript=/usr/libexec/qemu-server/pve-bridgedown,vhost=on' \
-device 'virtio-net-pci,mac=A2:C0:43:77:08:A0,netdev=net0,bus=pci.0,addr=0x12,id=net0,rx_queue_size=1024,tx_queue_size=256,bootindex=300' \
diff --git a/src/test/run_qemu_img_convert_tests.pl b/src/test/run_qemu_img_convert_tests.pl
index 8a0ad283..09456730 100755
--- a/src/test/run_qemu_img_convert_tests.pl
+++ b/src/test/run_qemu_img_convert_tests.pl
@@ -544,7 +544,7 @@ my $tests = [
"raw",
"--target-image-opts",
"/var/lib/vz/images/$vmid/vm-$vmid-disk-0.raw",
- "discard-no-unref=true,driver=qcow2,file.driver=file"
+ "cache-size=1073741824,discard-no-unref=true,driver=qcow2,file.driver=file"
. ",file.filename=/var/lib/vzsnapext/images/$vmid/vm-$vmid-disk-target.qcow2",
],
},
@@ -565,7 +565,7 @@ my $tests = [
"raw",
"--target-image-opts",
"/var/lib/vz/images/$vmid/vm-$vmid-disk-0.raw",
- "driver=zeroinit,file.discard-no-unref=true,file.driver=qcow2,file.file.driver=file"
+ "driver=zeroinit,file.cache-size=1073741824,file.discard-no-unref=true,file.driver=qcow2,file.file.driver=file"
. ",file.file.filename=/var/lib/vzsnapext/images/$vmid/vm-$vmid-disk-target.qcow2",
],
},
@@ -584,7 +584,7 @@ my $tests = [
"raw",
"--target-image-opts",
"/var/lib/vz/images/$vmid/vm-$vmid-disk-0.raw",
- "discard-no-unref=true,driver=qcow2,file.driver=host_device"
+ "cache-size=1073741824,discard-no-unref=true,driver=qcow2,file.driver=host_device"
. ",file.filename=/dev/pve/vm-$vmid-disk-target.qcow2",
],
},
--
2.47.2
[-- Attachment #2: Type: text/plain, Size: 160 bytes --]
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB
2025-08-13 13:46 [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB Alexandre Derumier via pve-devel
@ 2025-08-13 14:25 ` Fabian Grünbichler
2025-08-14 11:10 ` DERUMIER, Alexandre via pve-devel
0 siblings, 1 reply; 4+ messages in thread
From: Fabian Grünbichler @ 2025-08-13 14:25 UTC (permalink / raw)
To: Proxmox VE development discussion
On August 13, 2025 3:46 pm, Alexandre Derumier via pve-devel wrote:
>Currently, the qcow2 maximum cache-size is 32MB, enough to handle metadatas
>for a 256GB images with 65k cluster size.
>
>if cache-size is not big enough, performance are really bad
>
>This patch increase cache to 1GB, enough to handle 8TB image
>
>with default 32MB cache
>fio benchmark 4k randread/write:
>
>256GB image : 32MB cache : 40000 iops
>1TB image: 32MB cache: 2500 iops
>8TB image: 32MB cache: 2500 iops
>1TB image: 1G cache: 40000 iops
>8TB image: 1G cache: 40000 iops
>
>the cache-size value is a maximum value, memory is not reserved at vm start.
>Also, the metadatas not used are removed from the cache after 10min by defa=
>ult.
>
>https://gitlab.com/qemu-project/qemu/-/blob/master/docs/qcow2-cache.txt
>Signed-off-by: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
>---
> src/PVE/QemuServer/Blockdev.pm | 3 +++
> src/test/cfg2cmd/bootorder-empty.conf.cmd | 6 +++---
> src/test/cfg2cmd/bootorder-legacy.conf.cmd | 6 +++---
> src/test/cfg2cmd/bootorder.conf.cmd | 6 +++---
> .../cfg2cmd/cputype-icelake-client-deprecation.conf.cmd | 2 +-
> src/test/cfg2cmd/ide.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-ide.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-linux-hostpci-mapping.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-linux-hostpci-multifunction.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-linux-hostpci-template.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-linux-hostpci-x-pci-overrides.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-linux-hostpci.conf.cmd | 2 +-
> src/test/cfg2cmd/q35-simple.conf.cmd | 2 +-
> src/test/cfg2cmd/seabios_serial.conf.cmd | 2 +-
> src/test/cfg2cmd/simple-backingchain.conf.cmd | 4 ++--
> src/test/cfg2cmd/simple-virtio-blk.conf.cmd | 2 +-
> src/test/cfg2cmd/simple1-template.conf.cmd | 4 ++--
> src/test/cfg2cmd/simple1.conf.cmd | 2 +-
> src/test/run_qemu_img_convert_tests.pl | 6 +++---
> 19 files changed, 31 insertions(+), 28 deletions(-)
>
>diff --git a/src/PVE/QemuServer/Blockdev.pm b/src/PVE/QemuServer/Blockdev.pm
>index f5798cbf..895f1a6a 100644
>--- a/src/PVE/QemuServer/Blockdev.pm
>+++ b/src/PVE/QemuServer/Blockdev.pm
>@@ -381,6 +381,9 @@ my sub generate_format_blockdev {
> $blockdev->{'discard-no-unref'} =3D JSON::true if $format eq 'qcow=
>2';
> }
>=20
>+ #increase qcow2 maximum cache size to 1GB memory, enough to handle 8TB=
> disk image with 64k clusters.
>+ $blockdev->{'cache-size'} =3D 1073741824 if $format eq 'qcow2';
>+
> return $blockdev;
> }
have you benchmarked this? if so, did you compare it with using the
smaller cache-entry variant described in the file you linked:
https://gitlab.com/qemu-project/qemu/-/blob/master/docs/qcow2-cache.txt#L159
we also know the image size here, so we could use a capped, derived value?
what if the disk is resized? what about image files with bigger
clusters?
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB
2025-08-13 14:25 ` Fabian Grünbichler
@ 2025-08-14 11:10 ` DERUMIER, Alexandre via pve-devel
2025-08-14 14:14 ` DERUMIER, Alexandre via pve-devel
0 siblings, 1 reply; 4+ messages in thread
From: DERUMIER, Alexandre via pve-devel @ 2025-08-14 11:10 UTC (permalink / raw)
To: pve-devel, f.gruenbichler; +Cc: DERUMIER, Alexandre
[-- Attachment #1: Type: message/rfc822, Size: 14793 bytes --]
From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Subject: Re: [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB
Date: Thu, 14 Aug 2025 11:10:06 +0000
Message-ID: <dbd48cbf4e617b2b6e56cf7c73fbd71aaa9926b9.camel@groupe-cyllene.com>
>
> This patch increase cache to 1GB, enough to handle 8TB image
>
> with default 32MB cache
> fio benchmark 4k randread/write:
>
> 256GB image : 32MB cache : 40000 iops
> 1TB image: 32MB cache: 2500 iops
> 8TB image: 32MB cache: 2500 iops
> 1TB image: 1G cache: 40000 iops
> 8TB image: 1G cache: 40000 iops
>
>
>>have you benchmarked this?
yes, results are in this commit message (2500->40000iops with a 1TB
image with 64k cluster, same results with 128k cluster)
>> if so, did you compare it with using the
>>smaller cache-entry variant described in the file you linked:
Don't have tested it (I don't understand exactly this part to be
honest, but the default l2-cache-entry-size is already smaller, it's
4k, and we use 64k or 128k cluster size)
>>we also know the image size here, so we could use a capped, derived
>>value?
>>
>>what if the disk is resized?
One problem is disk resize, because the cache size can't be increase
without restart. That's why I think it's better to use a big cache
size.(It's really a max value)
>> what about image files with bigger clusters?
I have tried with bigger blocksize (so less metadatas, less memory),
but snapshot performance are not great. (for example, 1MB cluster, this
is 32MB sub-cluster on snapshot (vs 4k sub-cluster with 128k cluster),
with 4k write, you need to rewrite 32MB.
Maybe l2_extended2=on on main image could reduce the needed cache
memory, but from my tests it don't seem to help, I still need to
increase the cache (I'll try to retest it)
They are some good info in the suballocattion paper (including in the
video presentation)
https://blogs.igalia.com/berto/2020/12/03/subcluster-allocation-for-qcow2-images/
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* Re: [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB
2025-08-14 11:10 ` DERUMIER, Alexandre via pve-devel
@ 2025-08-14 14:14 ` DERUMIER, Alexandre via pve-devel
0 siblings, 0 replies; 4+ messages in thread
From: DERUMIER, Alexandre via pve-devel @ 2025-08-14 14:14 UTC (permalink / raw)
To: pve-devel, f.gruenbichler; +Cc: DERUMIER, Alexandre
[-- Attachment #1: Type: message/rfc822, Size: 16152 bytes --]
From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Subject: Re: [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB
Date: Thu, 14 Aug 2025 14:14:34 +0000
Message-ID: <d3d35e7701e478098349956797defae8340624d0.camel@groupe-cyllene.com>
some more tests with 1TB lvm qcow2:
------------------------------------
current patch
main image cluster_size=64k
--------------------------------------------------------
cluster_size=64k cache-size=1GB:
read 4k : 40k iops
write 4k: 25k iops
+ 1 snapshot cluster_size=128k+suballocated, cache=size=1G:
read 4k : 40kops iops
write 4k: 25k iops
main image cluster_size=1MB
------------------ -----------------
cluster_size=1MB cache-size=32mb:
read 4k : 40k iops
write 4k: 25k iops
---> bigger cluster need less cache
+ 1 snapshot cluster 128k+suballocated, cache-size=32MB:
read 4k : 3500 iops
write 4k: 2500iops
---> still not enough cache for 128k
cluster_size=1MB cache-size=1G:
read 4k : 40k iops
write 4k: 25k iops
+ 1 snapshot cluster_size=128k+suballocated, cache=size=1G:
read 4k : 40kops iops
write 4k: 20k iops
---> enough cache , performance are correct
cluster_size=1MB cache-size=32MB:
read 4k : 40k iops
write 4k: 25k iops
+ 1 snapshot cluster_size=1MB+suballocated, cache=size=32MB:
read 4k : 40kiops
write 4k: 3000iops
---> write performance are bad with big cluster size for snapshot
cluster_size=1MB cache-size=1GB:
read 4k : 40k iops
write 4k: 25k iops
+ 1 snapshot cluster_size=1MB+suballocated, cache=size=1GB:
read 4k : 40kiops
write 4k: 3000iops
---> write performance are bad with big cluster size for snapshot (even
with bigger cache)
So, snapshot really need small cluster size for good write performance,
to avoid big copy on write of backing image
Main image could have bigger cluster size, but I'm not sure of the
impact if // write occur on a specific cluster, maybe they could have
some kind of lock contention
some bench with enable sub allocated cluster on main image:
main image suballocated cluster_size=1MB cluster
------------------------------------------------
1MB cluster sub allocated 32mb cache : read 4k : 30k iops
wirte 4: 6k iops
1MB cluster sub allocated 1GB cache : read 4k : 30k iops
write 4: 6k iops
write performance is bad, better to avoid l2_extended=on on main image
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2025-08-13 13:46 [pve-devel] [PATCH qemu-server] qcow2: increase cache-size to 1GB Alexandre Derumier via pve-devel
2025-08-13 14:25 ` Fabian Grünbichler
2025-08-14 11:10 ` DERUMIER, Alexandre via pve-devel
2025-08-14 14:14 ` DERUMIER, Alexandre via pve-devel
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