From: Dave Chinner <david@fromorbit.com>
To: Waiman Long <Waiman.Long@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>,
linux-fsdevel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] dcache: make Oracle more scalable on large systems
Date: Sat, 23 Feb 2013 10:00:48 +1100 [thread overview]
Message-ID: <20130222230048.GP26694@dastard> (raw)
In-Reply-To: <5126F067.4040707@hp.com>
On Thu, Feb 21, 2013 at 11:13:27PM -0500, Waiman Long wrote:
> On 02/21/2013 07:13 PM, Andi Kleen wrote:
> >Dave Chinner<david@fromorbit.com> 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.
That seems to me like an application problem - poking at what the
kernel is doing via diagnostic interfaces so often that it gets in
the way of the kernel actually doing stuff is not a problem the
kernel can solve.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2013-02-22 23:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-19 18:50 [PATCH 0/4] dcache: make Oracle more scalable on large systems Waiman Long
2013-02-19 18:50 ` [PATCH 1/4] dcache: Don't take unncessary lock in d_count update Waiman Long
2013-02-19 18:50 ` [PATCH 2/4] dcache: introduce a new sequence read/write lock type Waiman Long
2013-02-19 18:50 ` [PATCH 3/4] dcache: change rename_lock to a sequence read/write lock Waiman Long
2013-02-19 18:50 ` Waiman Long
2013-02-19 18:50 ` Waiman Long
2013-02-19 18:50 ` [PATCH 4/4] dcache: don't need to take d_lock in prepend_path() Waiman Long
2013-02-21 23:38 ` [PATCH 0/4] dcache: make Oracle more scalable on large systems Dave Chinner
2013-02-22 0:13 ` Andi Kleen
2013-02-22 4:13 ` Waiman Long
2013-02-22 23:00 ` Dave Chinner [this message]
2013-02-23 0:13 ` Andi Kleen
2013-02-28 20:39 ` Waiman Long
2013-02-28 23:13 ` Waiman Long
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