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Date:	Tue, 16 Sep 2008 06:09:08 -0700 (PDT)
From:	Martin Knoblauch <knobi@...bisoft.de>
To:	linux-kernel@...r.kernel.org
Cc:	Peter zijlstra <a.p.zijlstra@...llo.nl>,
	Fengguang Wu <wfg@...l.ustc.edu.cn>
Subject: How to find out, what "pdflush" is working on

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.

Cheers
Martin
------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www:   http://www.knobisoft.de

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