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

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>

diff --git a/qm.adoc b/qm.adoc
index 644ece5775444c2b668c8aa53109b24f5a3218e2..900ecaeefe0e951049175dfb6577fcb301475825 100644 (file)
--- a/qm.adoc
+++ b/qm.adoc
@@ -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]]