Re: [Qemu-devel] =?gb18030?b?u9i4tKO6ILvYuLSjuiC72Li0o7ogu9i4tKO6ILvYuLSjuiC72Li0o7ogIHFlbXUgdm0gYmlnIG5ldHdvcmsgbGF0ZW5jeSB3aGVu?= =?gb18030?q?_met_heavy_io?=

[Josh Durgin <josh.durgin@inktank.com>]

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On 01/15/2014 10:12 PM, Ò¶ÉÜè¡ wrote:
> Hi Josh
>
> # strings /usr/bin/qemu-system-x86_64 | grep rbd_aio
> rbd_aio_write
> rbd_aio_flush
> rbd_aio_read
> rbd_aio_create_completion
> rbd_aio_release
> rbd_aio_discard
> rbd_aio_get_return_value
>
> So, librbd's asynchronous flush is being used.
>
> I set log settings, fetch the log and ping log with timestamped, all
> logs are in the attachment.

Excellent, thanks.

> It seems that I doesn't have permission to generate a new issue
> on tracker.ceph.com, when I click the 'Register' it show a 'internal
> error' page.

Seems to be working for me. In any case, I created
http://tracker.ceph.com/issues/7165 to track the problem.

Looking through the logs, it may have been already solved in
a couple commits after 0.67.5. Namely, the cache was starting the flush
of too much dirty data at once while holding a lock, preventing other
I/O from the guest from starting, and thus blocking the qemu thread
handling the I/O.

I added the relevant commits to the wip-objectcacher-flusher-dumpling
branch in ceph.git. Could you install librbd from that branch and see
if it fixes the problem? Instructions for getting these packages are:

http://ceph.com/docs/master/install/get-packages/#add-ceph-development

Thanks,
Josh