Re: [Qemu-devel] [PATCH 0/1] Fix iotests race condition by fixing block job rate limiting

[Max Reitz <mreitz@redhat.com>]

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On 28.06.2016 17:28, Sascha Silbe wrote:
> qemu-iotests #141 is relying on the test being able to operate on a
> block job it just started before further progress is being made on
> this block job. This fails regularly on some hosts because the time
> slice is just 100ms and it often takes longer than that to start the
> additional processes required to trigger the operation. It's
> particularly easy to reproduce under 100% CPU load.
> 
> I originally noticed and analysed this during 2.6 hard
> freeze. Eventually the legacy rate limiting code currently used by the
> block jobs will be replaced by the refactorings to use BlockBackends
> which have their own rate limiting implementation. There was some hope
> [1] this would land in 2.7, but since it's not in master yet (at least
> as of commit a01aef5d) I prepared an alternative fix that can go into
> 2.7.
> 
> Sascha Silbe (1):
>   Improve block job rate limiting for small bandwidth values
> 
>  block/commit.c           | 13 +++++--------
>  block/mirror.c           |  4 +++-
>  block/stream.c           | 12 ++++--------
>  include/qemu/ratelimit.h | 43 ++++++++++++++++++++++++++++++++++---------
>  4 files changed, 46 insertions(+), 26 deletions(-)
> 
> [1] mid:20160408123115.GH4700@noname.redhat.com
>     "Re: [Qemu-devel] [Qemu-block] [PATCH 6/7] qemu-iotests: 141:
>     reduce likelihood of race condition on systems with fast IO" by
>     Kevin Wolf <kwolf@redhat.com> on 2016-04-08.

Thanks Sascha, I've applied the patch to my block tree:

https://github.com/XanClic/qemu/commits/block

Max


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