linux-kernel - Re: [RFC PATCH -tip 0/2 v3] pagecache tracepoints proposal

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Date:	Sun, 14 Feb 2010 16:22:45 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Chris Frost <frost@...ucla.edu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Keiichi KII <k-keiichi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jason Baron <jbaron@...hat.com>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lwoodman@...hat.com" <lwoodman@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Tom Zanussi <tzanussi@...il.com>,
	"riel@...hat.com" <riel@...hat.com>,
	Munehiro Ikeda <m-ikeda@...jp.nec.com>,
	Atsushi Tsuji <a-tsuji@...jp.nec.com>
Subject: Re: [RFC PATCH -tip 0/2 v3] pagecache tracepoints proposal

* Balbir Singh <balbir@...ux.vnet.ibm.com> [2010-02-13 18:59:52]:

> * Wu Fengguang <fengguang.wu@...el.com> [2010-02-10 00:21:01]:
> 
> > > Here is a scratch patch to exercise the "object collections" idea :)
> > > 
> > > Interestingly, the pagecache walk is pretty fast, while copying out the trace
> > > data takes more time:
> > > 
> > >         # time (echo / > walk-fs)
> > >         (; echo / > walk-fs; )  0.01s user 0.11s system 82% cpu 0.145 total
> > > 
> > >         # time wc /debug/tracing/trace
> > >         4570 45893 551282 /debug/tracing/trace
> > >         wc /debug/tracing/trace  0.75s user 0.55s system 88% cpu 1.470 total
> > 
> > Ah got it: it takes much time to "print" the raw trace data.
> > 
> > > TODO:
> > > 
> > > correctness
> > > - show file path name
> > >   XXX: can trace_seq_path() be called directly inside TRACE_EVENT()?
> > 
> > OK, finished with the file name with d_path(). I choose not to mangle
> > the possible '\n' in file names, and simply show "?" for such files,
> > for the sake of speed.
> > 
> > Thanks,
> > Fengguang
> > ---
> > tracing: pagecache object collections
> > 
> > This dumps
> > - all cached files of a mounted fs  (the inode-cache)
> > - all cached pages of a cached file (the page-cache)
> > 
> > Usage and Sample output:
> > 
> > # echo /dev > /debug/tracing/objects/mm/pages/walk-fs
> > # tail /debug/tracing/trace
> >              zsh-2528  [000] 10429.172470: dump_inode: ino=889 size=0 cached=0 age=442 dirty=0 dev=0:18 file=/dev/console
> >              zsh-2528  [000] 10429.172472: dump_inode: ino=888 size=0 cached=0 age=442 dirty=7 dev=0:18 file=/dev/null
> >              zsh-2528  [000] 10429.172474: dump_inode: ino=887 size=40 cached=0 age=442 dirty=0 dev=0:18 file=/dev/shm
> >              zsh-2528  [000] 10429.172477: dump_inode: ino=886 size=40 cached=0 age=442 dirty=0 dev=0:18 file=/dev/pts
> >              zsh-2528  [000] 10429.172479: dump_inode: ino=885 size=11 cached=0 age=442 dirty=0 dev=0:18 file=/dev/core
> >              zsh-2528  [000] 10429.172481: dump_inode: ino=884 size=15 cached=0 age=442 dirty=0 dev=0:18 file=/dev/stderr
> >              zsh-2528  [000] 10429.172483: dump_inode: ino=883 size=15 cached=0 age=442 dirty=0 dev=0:18 file=/dev/stdout
> >              zsh-2528  [000] 10429.172486: dump_inode: ino=882 size=15 cached=0 age=442 dirty=0 dev=0:18 file=/dev/stdin
> >              zsh-2528  [000] 10429.172488: dump_inode: ino=881 size=13 cached=0 age=442 dirty=0 dev=0:18 file=/dev/fd
> >              zsh-2528  [000] 10429.172491: dump_inode: ino=872 size=13360 cached=0 age=442 dirty=0 dev=0:18 file=/dev
> > 
> > Here "age" is either age from inode create time, or from last dirty time.
> >
> 
> It would be nice to see mapped/unmapped information as well.
>

OK, I see you got mapcount, thanks!
 
-- 
	Three Cheers,
	Balbir
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