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

[Balbir Singh <balbir@linux.vnet.ibm.com>]

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

> * Wu Fengguang <fengguang.wu@intel.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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