From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [45.144.208.40]) by lore.proxmox.com (Postfix) with ESMTPS id B9FCE1FF0A7 for ; Wed, 19 Aug 2026 18:44:56 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 7BEDA2157B; Wed, 19 Aug 2026 18:44:54 +0200 (CEST) Message-ID: <87fd3468-358b-43cb-a035-9f38dfc11fe4@proxmox.com> Date: Wed, 19 Aug 2026 18:44:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH v2 qemu-server 0/5] bypass host page cache for restore on zvol To: pve-devel@lists.proxmox.com References: <20260819144642.453513-1-c.ebner@proxmox.com> Content-Language: en-US From: Jonas Theisen In-Reply-To: <20260819144642.453513-1-c.ebner@proxmox.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1787157865592 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.800 Adjusted score from AWL reputation of From: address DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment (newer systems) RCVD_IN_DNSWL_MED -2.3 Sender listed at https://www.dnswl.org/, medium trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: N27O4VFVZOFYQKUNDFARL3M3NGBTWHOD X-Message-ID-Hash: N27O4VFVZOFYQKUNDFARL3M3NGBTWHOD X-MailFrom: j.theisen@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 8/19/26 16:46, Christian Ebner wrote: > This patch series skips writing to the host page cache for restores > to zvols, with the intention to avoid potential I/O delay issues for > other ZFS-backed VMs during page writeback on certain setups, as > reported in enterprise support and reproduced internally. > > This patch series adds an optional no-cache parameter for pbs-restore > command invocation, setting the BDRV_O_NOCACHE flag for the block > device being restored to and sets `cache=none` for vma restores. > > Since this seems to affect only zvol's, conditionally set the flag only > during restores to storages with type `zfspool`. > > [snip] Tested this patch on a lab host with a restore from PBS on the same host. Seeing no relevant I/O delays on a zvol on the same pool. VMs hosted on the same pool also experience only marginal delays. -- Tested-by: Jonas Theisen