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Date: Wed, 17 Sep 2008 01:11:17 -0700 (PDT) From: Martin Knoblauch <knobi@...bisoft.de> To: Chris Snook <csnook@...hat.com> Cc: linux-kernel@...r.kernel.org, Peter zijlstra <a.p.zijlstra@...llo.nl>, Fengguang Wu <wfg@...l.ustc.edu.cn> Subject: Re: How to find out, what "pdflush" is working on ----- Original Message ---- > From: Chris Snook <csnook@...hat.com> > To: Martin Knoblauch <knobi@...bisoft.de> > Cc: linux-kernel@...r.kernel.org; Peter zijlstra <a.p.zijlstra@...llo.nl>; Fengguang Wu <wfg@...l.ustc.edu.cn> > Sent: Tuesday, September 16, 2008 9:07:29 PM > Subject: Re: How to find out, what "pdflush" is working on > > Martin Knoblauch wrote: > > Hi, > > > > I find the following comment in mm/pdflush.c > > > > /* * The pdflush threads are worker threads for writing back dirty data. * > > Ideally, we'd like one thread per active disk spindle. But the disk * > > topology is very hard to divine at this level. Instead, we take * care in > > various places to prevent more than one pdflush thread from * performing > > writeback against a single filesystem. pdflush threads * have the PF_FLUSHER > > flag set in current->flags to aid in this. */ > > > > Is there a way to find out what a certain instance of "pdflush" is working > > on? Like which block-device or which fliesystem it is writing to? I am still > > (2.6.27) trying to track down why writing a single file can make linux very > > sluggish and unresponsive. If that happens I usually see all possible 8 > > "pdflush" threads being in "D"-state. According to above comment only one of > > them should be really busy. > > The key word is "ideally". We'd like it to work that way, but it doesn't. > Patches to fix this are welcome. > Now, I am pretty much aware that apparently things are not "ideal". Therefore my question. Because before doing patches, one has to analyze. Cheers Martin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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