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 3ADAC1FF0B6 for ; Wed, 19 Aug 2026 10:32:25 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 1F4312152F; Wed, 19 Aug 2026 10:32:21 +0200 (CEST) From: Maximiliano Sandoval To: pve-devel@lists.proxmox.com Subject: [PATCH docs 1/1] qm: clarify when the iothreads options takes into effect Date: Wed, 19 Aug 2026 10:32:11 +0200 Message-ID: <20260819083214.115093-1-m.sandoval@proxmox.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1787128310551 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.984 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: 2RFC47K2UAPKSJAXSGUPKHPHF5EASVXL X-Message-ID-Hash: 2RFC47K2UAPKSJAXSGUPKHPHF5EASVXL X-MailFrom: m.sandoval@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: The main point addressed is that the "VirtIO Block" bus controller type was referred as "VirtIO". This can be a source of confusion since the are multiple controllers for different components provided by VirtIO. VirtIO SCSI is listed before VirtIO Block as a soft-recommendation. We use the same terms as the web UI, modulo capitalization for "Bus/Device" and "SCSI Controller". Signed-off-by: Maximiliano Sandoval --- qm.adoc | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/qm.adoc b/qm.adoc index 5b46cdc..51935ea 100644 --- a/qm.adoc +++ b/qm.adoc @@ -337,14 +337,18 @@ Note that *SSD emulation* is not supported on *VirtIO Block* drives. [[qm_hard_disk_iothread]] IO Thread ^^^^^^^^^ -The option *IO Thread* can only be used when using a disk with the *VirtIO* -controller, or with the *SCSI* controller, when the emulated controller type is -*VirtIO SCSI single*. With *IO Thread* enabled, QEMU creates one I/O thread per -storage controller rather than handling all I/O in the main event loop or vCPU -threads. One benefit is better work distribution and utilization of the -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. +The *IO thread* option can only be used when using a disk with one of the +following bus/device controllers: + +* *SCSI*, if the emulated SCSI controller type is *VirtIO SCSI single*, or +* *VirtIO Block* + +With *IO thread* enabled, QEMU creates one I/O thread per storage controller +rather than handling all I/O in the main event loop or vCPU threads. One benefit +is better work distribution and utilization of the 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_cpu]] CPU -- 2.47.3