linux-kernel - Re: [patch 09/17] LTTng instrumentation

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Date:	Wed, 16 Jul 2008 10:37:19 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <mhiramat@...hat.com>, linux-mm@...ck.org,
	Dave Hansen <haveblue@...ibm.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Hideo AOKI <haoki@...hat.com>,
	Takashi Nishiie <t-nishiie@...css.fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
Subject: Re: [patch 09/17] LTTng instrumentation - filemap

* Peter Zijlstra (peterz@...radead.org) wrote:
> On Tue, 2008-07-15 at 18:26 -0400, Mathieu Desnoyers wrote:
> > plain text document attachment (lttng-instrumentation-filemap.patch)
> > Instrumentation of waits caused by memory accesses on mmap regions.
> > 
> > Those tracepoints are used by LTTng.
> > 
> > About the performance impact of tracepoints (which is comparable to markers),
> > even without immediate values optimizations, tests done by Hideo Aoki on ia64
> > show no regression. His test case was using hackbench on a kernel where
> > scheduler instrumentation (about 5 events in code scheduler code) was added.
> > See the "Tracepoints" patch header for performance result detail.
> > 
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> > CC: linux-mm@...ck.org
> > CC: Dave Hansen <haveblue@...ibm.com>
> > CC: Masami Hiramatsu <mhiramat@...hat.com>
> > CC: 'Peter Zijlstra' <peterz@...radead.org>
> > CC: "Frank Ch. Eigler" <fche@...hat.com>
> > CC: 'Ingo Molnar' <mingo@...e.hu>
> > CC: 'Hideo AOKI' <haoki@...hat.com>
> > CC: Takashi Nishiie <t-nishiie@...css.fujitsu.com>
> > CC: 'Steven Rostedt' <rostedt@...dmis.org>
> > CC: Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
> > ---
> >  include/trace/filemap.h |   13 +++++++++++++
> >  mm/filemap.c            |    3 +++
> >  2 files changed, 16 insertions(+)
> > 
> > Index: linux-2.6-lttng/mm/filemap.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/mm/filemap.c	2008-07-15 14:51:50.000000000 -0400
> > +++ linux-2.6-lttng/mm/filemap.c	2008-07-15 15:14:46.000000000 -0400
> > @@ -33,6 +33,7 @@
> >  #include <linux/cpuset.h>
> >  #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
> >  #include <linux/memcontrol.h>
> > +#include <trace/filemap.h>
> >  #include "internal.h"
> >  
> >  /*
> > @@ -541,9 +542,11 @@ void wait_on_page_bit(struct page *page,
> >  {
> >  	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
> >  
> > +	trace_filemap_wait_start(page, bit_nr);
> >  	if (test_bit(bit_nr, &page->flags))
> >  		__wait_on_bit(page_waitqueue(page), &wait, sync_page,
> >  							TASK_UNINTERRUPTIBLE);
> > +	trace_filemap_wait_end(page, bit_nr);
> >  }
> >  EXPORT_SYMBOL(wait_on_page_bit);
> 
> I don't like the trace_filemap_wait_* naming..
> 

Me neither :)

> trace_wait_on_page_* might make more sense
> 

Yep, agreed,

Mathieu

> > Index: linux-2.6-lttng/include/trace/filemap.h
> > ===================================================================
> > --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> > +++ linux-2.6-lttng/include/trace/filemap.h	2008-07-15 15:14:46.000000000 -0400
> > @@ -0,0 +1,13 @@
> > +#ifndef _TRACE_FILEMAP_H
> > +#define _TRACE_FILEMAP_H
> > +
> > +#include <linux/tracepoint.h>
> > +
> > +DEFINE_TRACE(filemap_wait_start,
> > +	TPPROTO(struct page *page, int bit_nr),
> > +	TPARGS(page, bit_nr));
> > +DEFINE_TRACE(filemap_wait_end,
> > +	TPPROTO(struct page *page, int bit_nr),
> > +	TPARGS(page, bit_nr));
> > +
> > +#endif
> > 
> 

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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