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qm: IO thread: be more precise about how QEMU handles IO

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Reported in the community forum[0].

The setting can already help with a single disk. Without the option,
there is not one IO thread as the old wording suggested, but IO is
handled in the main event loop or vCPU threads (see the kvm man page).

[0]: https://forum.proxmox.com/threads/118390/post-518532

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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Fiona Ebner 2022-12-20 12:24:22 +01:00 committed by Thomas Lamprecht
parent af9941ba2b
commit 4c7a47cf0e
1 changed files with 5 additions and 6 deletions
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@ -249,12 +249,11 @@ 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 this enabled, QEMU creates one I/O thread per storage controller,
rather than a single thread for all I/O. This can increase performance when
multiple disks are used and each disk has its own storage controller.
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. This can increase performance, because of improved work distribution.
[[qm_cpu]]