Re: Slower performance after enabling async io on Oracle Linux
From: joel garry <joel-garry_at_home.com>
Date: Mon, 14 May 2012 09:17:31 -0700 (PDT)
Message-ID: <01eb7374-776f-4288-8342-1ce234a5054a_at_ri8g2000pbc.googlegroups.com>
On May 14, 2:03 am, Matthias Hoys <matthias.h..._at_gmail.com> wrote:
> Hello,
>
> Platform is Oracle Linux 6.2 64-bit with Oracle 11.2.0.3 64-bit.
>
> After enabling async io, I see slower performance for data pump exports, RMAN backups and long-running queries (between 10 and 15% slower).
>
> I enabled async io with:
>
> ALTER SYSTEM SET FILESYSTEMIO_OPTIONS=SETALL SCOPE=SPFILE;
> aio-nr is 19052 and aio-max-nr is 1048576. Storage is on iSCSI.
>
> Anyone else with the same experience? Is extra tuning for async io possible on Oracle Linux?
>
> Thanks,
> Matthias Hoys
Date: Mon, 14 May 2012 09:17:31 -0700 (PDT)
Message-ID: <01eb7374-776f-4288-8342-1ce234a5054a_at_ri8g2000pbc.googlegroups.com>
On May 14, 2:03 am, Matthias Hoys <matthias.h..._at_gmail.com> wrote:
> Hello,
>
> Platform is Oracle Linux 6.2 64-bit with Oracle 11.2.0.3 64-bit.
>
> After enabling async io, I see slower performance for data pump exports, RMAN backups and long-running queries (between 10 and 15% slower).
>
> I enabled async io with:
>
> ALTER SYSTEM SET FILESYSTEMIO_OPTIONS=SETALL SCOPE=SPFILE;
> aio-nr is 19052 and aio-max-nr is 1048576. Storage is on iSCSI.
>
> Anyone else with the same experience? Is extra tuning for async io possible on Oracle Linux?
>
> Thanks,
> Matthias Hoys
Well, it could be simply squeezing the bottleneck balloon, where something goes faster and consequently something depending on it slows down (for example, more cpu required to service more I/O). Some hugepages misconfiguration could have strange consequences simply from wasted memory, too.
Also see, for example, http://blog.tanelpoder.com/2010/11/23/asynch-descriptor-resize-wait-event-in-oracle/
fixed by your patch, but the linux/oracle async interaction is so
delicate, you may be seeing something unfixed by the patch. Any
errors like
http://www.freelists.org/post/oracle-l/WARNINGio-submit-failed-due-to-kernel-limitations-MAXAIO-for-process128-pending-aio127,2
?
jg
-- _at_home.com is bogus. http://www.utsandiego.com/news/2012/may/10/hackers-taking-aim-small-medium-businesses/Received on Mon May 14 2012 - 11:17:31 CDT