From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 9B54B99118 for ; Mon, 13 Nov 2023 18:11:16 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 7C3C116486 for ; Mon, 13 Nov 2023 18:10:46 +0100 (CET) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS for ; Mon, 13 Nov 2023 18:10:44 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id A84E94105B for ; Mon, 13 Nov 2023 18:10:44 +0100 (CET) From: Friedrich Weber To: pve-devel@lists.proxmox.com Date: Mon, 13 Nov 2023 18:09:15 +0100 Message-Id: <20231113170916.184994-2-f.weber@proxmox.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231113170916.184994-1-f.weber@proxmox.com> References: <20231113170916.184994-1-f.weber@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL -0.130 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - Subject: [pve-devel] [PATCH docs 1/2] pci passthrough: mention incompatibility with ballooning X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Nov 2023 17:11:16 -0000 When using PCI(e) passthrough, setting a minimum amount of memory does not have any effect, which may be surprising to users [0]. Add a note to the PCI(e) passthrough section, and reference it in the ballooning section. [0] https://forum.proxmox.com/threads/134202/ Signed-off-by: Friedrich Weber --- qm-pci-passthrough.adoc | 10 ++++++++++ qm.adoc | 5 +++++ 2 files changed, 15 insertions(+) diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc index 1f68721..406156d 100644 --- a/qm-pci-passthrough.adoc +++ b/qm-pci-passthrough.adoc @@ -20,6 +20,16 @@ PCI speeds. Passing through devices as PCIe just sets a flag for the guest to tell it that the device is a PCIe device instead of a "really fast legacy PCI device". Some guest applications benefit from this. +xref:qm_ballooning[Automatic memory allocation (ballooning)] is not possible +when using PCI(e) passthrough. As the PCI device may use DMA (Direct Memory +Access), QEMU needs to map the complete guest memory on VM startup. Hence, the +QEMU process will use at least the (maximum) configured amount of VM memory and +setting a minimum amount does not have any effect. When using PCI(e) +passthrough, it is recommended to set memory and minimum memory to the same +amount and keep the balloning device enabled. However, keep in mind that the +memory consumption reported in the GUI for the VM may be much lower than the +memory consumption of the QEMU process. + General Requirements ~~~~~~~~~~~~~~~~~~~~ diff --git a/qm.adoc b/qm.adoc index b7938d7..cbc5e0d 100644 --- a/qm.adoc +++ b/qm.adoc @@ -623,6 +623,7 @@ it (like for debugging purposes), simply uncheck *Ballooning Device* or set in the configuration. +[[qm_ballooning]] .Automatic Memory Allocation // see autoballoon() in pvestatd.pm @@ -659,6 +660,10 @@ systems. When allocating RAM to your VMs, a good rule of thumb is always to leave 1GB of RAM available to the host. +When using PCI(e) passthrough, setting a minimum amount of memory does not have +any effect, see the section on xref:qm_pci_passthrough[PCI(e) passthrough] for +more details. + [[qm_network_device]] Network Device -- 2.39.2