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SubjectRe: [patch 09/17] LTTng instrumentation - filemap
* Peter Zijlstra (peterz@infradead.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@polymtl.ca>
> > CC: linux-mm@kvack.org
> > CC: Dave Hansen <haveblue@us.ibm.com>
> > CC: Masami Hiramatsu <mhiramat@redhat.com>
> > CC: 'Peter Zijlstra' <peterz@infradead.org>
> > CC: "Frank Ch. Eigler" <fche@redhat.com>
> > CC: 'Ingo Molnar' <mingo@elte.hu>
> > CC: 'Hideo AOKI' <haoki@redhat.com>
> > CC: Takashi Nishiie <t-nishiie@np.css.fujitsu.com>
> > CC: 'Steven Rostedt' <rostedt@goodmis.org>
> > CC: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.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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