From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Madhusudhan" Subject: RE: mmcqd cpu utilization Date: Wed, 2 Sep 2009 14:57:27 -0500 Message-ID: <00ae01ca2c07$98d416f0$544ff780@am.dhcp.ti.com> References: <007301ca2bf2$2888e2a0$544ff780@am.dhcp.ti.com> <20090902194036.07c1f72c@mjolnir.ossman.eu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090902194036.07c1f72c@mjolnir.ossman.eu> Sender: linux-omap-owner@vger.kernel.org To: 'Pierre Ossman' Cc: linux-mmc@vger.kernel.org, linux-omap@vger.kernel.org, hch@lst.de List-Id: linux-mmc@vger.kernel.org > -----Original Message----- > From: Pierre Ossman [mailto:pierre@ossman.eu] > Sent: Wednesday, September 02, 2009 12:41 PM > To: Madhusudhan > Cc: linux-mmc@vger.kernel.org; linux-omap@vger.kernel.org; hch@lst.de > Subject: Re: mmcqd cpu utilization > > On Wed, 2 Sep 2009 12:23:59 -0500 > "Madhusudhan" wrote: > > > Hi, > > > > Has anyone monitored the cpu utilization percentage when a MMC/SD card > is in > > use? I have noticed that mmc_queue_thread "mmcqd" consumes a lot of cpu > > cycles in a periodic fashion. What I mean here is that I see spikes of > high > > cpu utilization due to mmcqd. There will a cp or similar which will be > > already consuming cpu to transfer data to the MMC/SD device. Further > mmcqd > > increases that load randomly to a high number. > > > > Has anyone seen similar behavior? Any thoughts? > > > > My guess would be that the omap driver doesn't (cannot?) use the > hardware to wait for busy to end, so the system must poll. > So your guess hints probably at "wait_for_completion(&complete)". Am I correct? Regards, Madhu > Anything better than that guess will require some profiling. :) > > Rgds > -- > -- Pierre Ossman > > WARNING: This correspondence is being monitored by the > Swedish government. Make sure your server uses encryption > for SMTP traffic and consider using PGP for end-to-end > encryption.