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    SubjectRe: [patch 09/17] LTTng instrumentation - filemap
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    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..

    trace_wait_on_page_* might make more sense

    > 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
    >



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