* [Qemu-devel] About the IO queue inside qemu
@ 2013-10-02 6:28 Yaodong Yang
2013-10-02 10:16 ` Stefan Hajnoczi
0 siblings, 1 reply; 2+ messages in thread
From: Yaodong Yang @ 2013-10-02 6:28 UTC (permalink / raw)
To: qemu-devel@nongnu.org, qemu-discuss@nongnu.org; +Cc: Yaodong Yang
Hi all,
I'm wondering is there any io queue inside qemu? Is there any IO scheduling inside it? I notice that there is an IO track feature inside block.c, but I do not know the purpose of it. Could someone explain it for me? Thanks a lot!
Yaodong
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] About the IO queue inside qemu
2013-10-02 6:28 [Qemu-devel] About the IO queue inside qemu Yaodong Yang
@ 2013-10-02 10:16 ` Stefan Hajnoczi
0 siblings, 0 replies; 2+ messages in thread
From: Stefan Hajnoczi @ 2013-10-02 10:16 UTC (permalink / raw)
To: Yaodong Yang; +Cc: qemu-devel@nongnu.org, qemu-discuss@nongnu.org
On Wed, Oct 02, 2013 at 01:28:11AM -0500, Yaodong Yang wrote:
> I'm wondering is there any io queue inside qemu? Is there any IO scheduling inside it? I notice that there is an IO track feature inside block.c, but I do not know the purpose of it. Could someone explain it for me? Thanks a lot!
There are two queues:
1. Throttled requests. Used by the I/O throttling feature (-drive
iops=5000). Requests need to be suspended until there is enough
budget for them.
2. Tracked requests. This is a generic queue that is used by the
copy-on-read feature to prevent corruption when the guest writes to a
sector that is currently being copied.
There is also an API to batch writes so they can be merged. virtio-blk
uses this and may therefore change the I/O pattern.
Stefan
^ permalink raw reply [flat|nested] 2+ messages in thread
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