Re: [PATCH 0/4] dcache: make Oracle more scalable on large systems

[Waiman Long]

On 02/21/2013 07:13 PM, Andi Kleen wrote:
> Dave Chinner<david@xxxxxxxxxxxxx>  writes:
>
> > On Tue, Feb 19, 2013 at 01:50:55PM -0500, Waiman Long wrote:
> > > It was found that the Oracle database software issues a lot of call
> > > to the seq_path() kernel function which translates a (dentry, mnt)
> > > pair to an absolute path. The seq_path() function will eventually
> > > take the following two locks:
> > Nobody should be doing reverse dentry-to-name lookups in a quantity
> > sufficient for it to become a performance limiting factor. What is
> > the Oracle DB actually using this path for?
> Yes calling d_path frequently is usually a bug elsewhere.
> Is that through /proc ?
>
> -Andi
A sample strace of Oracle indicates that it opens a lot of /proc 
filesystem files such as the stat, maps, etc many times while running. 
Oracle has a very detailed system performance reporting infrastructure 
in place to report almost all aspect of system performance through its 
AWR reporting tool or the browser-base enterprise manager. Maybe that is 
the reason why it is hitting this performance bottleneck.

Regards,
Longman
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