From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH 0/4] dcache: make Oracle more scalable on large systems Date: Thu, 21 Feb 2013 23:13:27 -0500 Message-ID: <5126F067.4040707@hp.com> References: <1361299859-27056-1-git-send-email-Waiman.Long@hp.com> <20130221233818.GM26694@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Dave Chinner , linux-fsdevel@vger.kernel.org, Alexander Viro , linux-kernel@vger.kernel.org To: Andi Kleen Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 02/21/2013 07:13 PM, Andi Kleen wrote: > Dave Chinner 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