dozens of xfsaild threads

[Erik Knight]

Hi Ben,

Thanks for the help. The workload is a typical ETL processing. Building a
DataWarehouse. I'll get you the rest of that information as soon as I can
the tip about the metadata is already very interesting.

Thanks,
Erik


On Fri, Feb 22, 2013 at 9:25 PM, Ben Myers <bpm at sgi.com> wrote:

> Hi Erik,
>
> On Fri, Feb 22, 2013 at 02:04:17PM +0100, Erik Knight wrote:
> > We've recently noticed that our system is experiencing extreme
> performance
> > problems when running large workloads. The problem seems to come from
> > excessive System CPU time. Specifically dozens of xfsaild threads. We
> used
> > to have SSD drives but recently switched to HDD, so some of us are
> thinking
> > that there may be a configuration issue within XFS that is optimized for
> > SSD but performs terribly slow on HDD.
> >
> > Can anyone explain what these threads do, what would cause so many of
> them
> > to be running simultaneously or consume so much CPU?
>
> AIL stands for Active Item List.  These guys sync metadata which has been
> logged to its final location on disk.  You'll have one daemon per
> filesystem.
>
> If you have a very metadata intensive workload they could get a workout.
>  It
> would help to know a bit more about your workload and configuration.  Can
> you
> provide the relevant information listed here?
>
>
> http://www.xfs.org/index.php/XFS_FAQ#Q:_What_information_should_I_include_when_reporting_a_problem.3F
>
> Regards,
>         Ben
>
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