Re: OT - Blog entry on hugepages

From: Rich Jesse <>
Date: Wed, 4 Apr 2012 16:10:08 -0500 (CDT)
Message-ID: <>

Hey Kyle,

> Does anyone have metrics to identify memory access problems on AIX other
> than paging and scanning stats that might be solved with largepages?
> Recently an AIX customer was seeing slow I/Os from an NFS filer but fast
> local I/O response times. Of course the customer blamed the NFS filer, but
> the filer reported constant speeds during good periods as well as bad. I

Was CPU consistent between the tests?

Does the init.ora filesystemio_options='SETALL'? I'm not sure how that affects the NFS mount, but for JFS2 mounts, that will cause Oracle to automagically use CIO (Ora10g and up) and also AIO, if enabled, IIRC. Oracle does this regardless of the mount options specified in /etc/filesystems, again for JFS2.

I'm theorizing that if CIO's not used, there could be Oracle data files in the filecache of the local storage, which could result in higher CPU while still appearing as PIO to Oracle. This would also depend on the VMO filecache settings of minperm/maxperm/maxclient. I watch the filecache constantly in AIX's excellent nmon in the memory window, as well as a vmstat monitoring script containing:

vmstat -v|grep -E 'numperm|file pages'

Hope this drivel helps! I don't claim to be an expert in this, but have been delving into this stuff now to help me determine how big I can make my buffer cache w/o causing AIX (v5.3) paging.



Received on Wed Apr 04 2012 - 16:10:08 CDT

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