From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [IPv6:2a0f:8001:1:32::40]) by lore.proxmox.com (Postfix) with ESMTPS id D0E911FF0E9 for ; Thu, 16 Jul 2026 10:25:34 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 10970214DD; Thu, 16 Jul 2026 10:25:22 +0200 (CEST) Message-ID: <4fd61349-cf66-4769-bd1f-98e0e095866d@proxmox.com> Date: Thu, 16 Jul 2026 10:25:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH pve-docs 3/3] partially fix #1989: qm: document qcow2 cache size config To: Erik Fastermann , pve-devel@lists.proxmox.com References: <20260605153512.265703-1-e.fastermann@proxmox.com> <20260605153512.265703-4-e.fastermann@proxmox.com> Content-Language: en-US From: Dominik Csapak In-Reply-To: <20260605153512.265703-4-e.fastermann@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: 1784190297217 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.308 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_LOW -0.7 Sender listed at https://www.dnswl.org/, low 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: XY3P6XKIERVJZEJG5J5XWPFDVRUEL7F7 X-Message-ID-Hash: XY3P6XKIERVJZEJG5J5XWPFDVRUEL7F7 X-MailFrom: d.csapak@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 6/5/26 5:35 PM, Erik Fastermann wrote: > Add a new subsection to document the new qcow2 cache config options. > > Signed-off-by: Erik Fastermann > --- > qm.adoc | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/qm.adoc b/qm.adoc > index e6b7918..2f1e7d4 100644 > --- a/qm.adoc > +++ b/qm.adoc > @@ -341,6 +341,16 @@ underlying storage. Another benefit is reduced latency (hangs) in the guest for > very I/O-intensive host workloads, since neither the main thread nor a vCPU > thread can be blocked by disk I/O. > > +[[qm_hard_disk_qcow2_cache]] > +Cache Size (qcow2) > +^^^^^^^^^^^^^^^^^^ > +Fine-tuning the qcow2 L2/refcount cache behavior can provide significant > +performance gains. See the > +https://gitlab.com/qemu-project/qemu/-/blob/master/docs/qcow2-cache.txt[QEMU documentation] > +for a detailed explanation of these options. You can either configure the cache > +size directly or let Proxmox VE automatically choose a cache size based on the > +disk image size. All other options can be managed with the API. > + i would have liked a short explanation how the auto-sizing algorithm works. I guess as an admin this would be the first thing i'd ask if i see an 'auto' option (e.g. to gauge the memory requirements for my vms). > [[qm_cpu]] > CPU > ~~~