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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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