> Hi,
>
> The previous two postings can be found here:
>
http://lkml.org/lkml/2010/4/1/344
> and here:
>
http://lkml.org/lkml/2010/4/7/325
>
> The basic problem is that, when running iozone on smallish files (up to
> 8MB in size) and including fsync in the timings, deadline outperforms
> CFQ by a factor of about 5 for 64KB files, and by about 10% for 8MB
> files. From examining the blktrace data, it appears that iozone will
> issue an fsync() call, and subsequently wait until its CFQ timeslice
> has expired before the journal thread can run to actually commit data to
> disk.
>
> The approach taken to solve this problem is to implement a blk_yield call,
> which tells the I/O scheduler not to idle on this process' queue. The call
> is made from the jbd[2] log_wait_commit function.
>
> This patch set addresses previous concerns that the sync-noidle workload
> would be starved by keeping track of the average think time for that
> workload and using that to decide whether or not to yield the queue.
>
> My testing showed nothing but improvements for mixed workloads, though I
> wouldn't call the testing exhaustive. I'd still very much like feedback
> on the approach from jbd/jbd2 developers. Finally, I will continue to do
> performance analysis of the patches.
