[pve-devel] [PATCH v2 qemu-server] fix #2570: add 'keephugepages' config

[pve-devel] [PATCH v2 qemu-server] fix #2570: add 'keephugepages' config

[Stefan Reiter]

We already keep hugepages if they are created with the kernel
commandline (hugepagesz=x hugepages=y), but some setups (specifically
hugepages across multiple NUMA nodes) cannot be configured that way.
Since we always clear these hugepages at VM shutdown, rebooting a VM
that uses them might not work, since the requested count might not be
available anymore by the time we want to use them (also, we would then
no longer allocate them correctly on the NUMA nodes).

Add a 'keephugepages' parameter to skip cleanup and simply leave them
untouched.

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---

v2:
* rebase

 PVE/QemuServer.pm | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index a5ee8e2..d2a20b6 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -441,6 +441,14 @@ EODESC
 	description => "Enable/disable hugepages memory.",
 	enum => [qw(any 2 1024)],
     },
+    keephugepages => {
+	optional => 1,
+	type => 'boolean',
+	default => 0,
+	description => "Use together with hugepages. If enabled, hugepages will"
+		     . " not be deleted after VM shutdown and can be used for"
+		     . " subsequent starts.",
+    },
     vcpus => {
 	optional => 1,
 	type => 'integer',
@@ -5034,11 +5042,13 @@ sub vm_start_nolock {
 
 	    eval { $run_qemu->() };
 	    if (my $err = $@) {
-		PVE::QemuServer::Memory::hugepages_reset($hugepages_host_topology);
+		PVE::QemuServer::Memory::hugepages_reset($hugepages_host_topology)
+		    if !$conf->{keephugepages};
 		die $err;
 	    }
 
-	    PVE::QemuServer::Memory::hugepages_pre_deallocate($hugepages_topology);
+	    PVE::QemuServer::Memory::hugepages_pre_deallocate($hugepages_topology)
+		if !$conf->{keephugepages};
 	};
 	eval { PVE::QemuServer::Memory::hugepages_update_locked($code); };
 
-- 
2.20.1

[pve-devel] applied: [PATCH v2 qemu-server] fix #2570: add 'keephugepages' config

[Thomas Lamprecht]

On 02.09.20 11:03, Stefan Reiter wrote:
> We already keep hugepages if they are created with the kernel
> commandline (hugepagesz=x hugepages=y), but some setups (specifically
> hugepages across multiple NUMA nodes) cannot be configured that way.
> Since we always clear these hugepages at VM shutdown, rebooting a VM
> that uses them might not work, since the requested count might not be
> available anymore by the time we want to use them (also, we would then
> no longer allocate them correctly on the NUMA nodes).
> 
> Add a 'keephugepages' parameter to skip cleanup and simply leave them
> untouched.
> 
> Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
> ---
> 
> v2:
> * rebase
> 
>  PVE/QemuServer.pm | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
>

applied, thanks!