Re: [RFC, PATCH 0/2] Reworking seeky detection for 2.6.34

[Jens Axboe <jens.axboe@oracle.com>]

On Sat, Feb 27 2010, Corrado Zoccolo wrote:
> 
> Hi, I'm resending the rework seeky detection patch, together with 
> the companion patch for SSDs, in order to get some testing on more
> hardware.
> 
> The first patch in the series fixes a regression introduced in 2.6.33
> for random mmap reads of more than one page, when multiple processes
> are competing for the disk.
> There is at least one HW RAID controller where it reduces performance,
> though (but this controller generally performs worse with CFQ than
> with NOOP, probably because it is performing non-work-conserving 
> I/O scheduling inside), so more testing on RAIDs is appreciated.
> 
> The second patch changes the seeky detection logic to be meaningful
> also for SSDs. A seeky request is one that doesn't utilize the full
> bandwidth for the device. For SSDs, this happens for small requests,
> regardless of their location.
> With this change, the grouping of "seeky" requests done by CFQ can
> result in a fairer distribution of disk service time among processes.

Thanks, I have applied this.

-- 
Jens Axboe