Re: Slower performance after enabling async io on Oracle Linux

From: Matthias Hoys <>
Date: Tue, 15 May 2012 06:01:51 -0700 (PDT)
Message-ID: <18420171.890.1337086911679.JavaMail.geo-discussion-forums_at_vbli11>

On Monday, May 14, 2012 6:17:31 PM UTC+2, joel garry wrote:
> 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,
> 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
> ?
> jg
> --
> is bogus.

Using vmstat/top, I don't see anything which could indicate a CPU bottleneck. I didn't configure hugepages, since this is a small Linux box with only 2GB SGA. When async io is enabled, I only see very few of the "asynch descriptor resize" waits. When filesystemio_options is set to NONE and disk_asynch_io is set to TRUE, the following warnings occur in archive logging trace files: "Log read is SYNCHRONOUS though disk_asynch_io is enabled!". There are no "maxaio kernel limitation" errors...

Matthias Received on Tue May 15 2012 - 08:01:51 CDT

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