linux-kernel - Re: [PATCH] Add tracepoints to track pagecache transition

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Date:	Tue, 17 Feb 2009 20:04:28 +0900
From:	Atsushi Tsuji <a-tsuji@...jp.nec.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, Jason Baron <jbaron@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Kazuto Miyoshi <miyoshi@...ux.bs1.fc.nec.co.jp>,
	rostedt@...dmis.org, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: [PATCH] Add tracepoints to track pagecache transition

Peter Zijlstra wrote:
> On Tue, 2009-02-17 at 18:00 +0900, Atsushi Tsuji wrote:
> 
>> The below patch adds instrumentation for pagecache.
> 
> And somehow you forgot to CC any of the mm people.. ;-)

Hi Peter,

Ah, sorry.
Thank you for adding to CC list.

>> +DECLARE_TRACE(filemap_add_to_page_cache,
>> +	TPPROTO(struct address_space *mapping, pgoff_t offset),
>> +	TPARGS(mapping, offset));
>> +DECLARE_TRACE(filemap_remove_from_page_cache,
>> +	TPPROTO(struct address_space *mapping),
>> +	TPARGS(mapping));
> 
> This is rather asymmetric, why don't we care about the offset for the
> removed page?
> 

Indeed.
I added the offset to the argument for the removed page and resend fixed patch.

Signed-off-by: Atsushi Tsuji <a-tsuji@...jp.nec.com>
---
diff --git a/include/trace/filemap.h b/include/trace/filemap.h
new file mode 100644
index 0000000..a17dc92
--- /dev/null
+++ b/include/trace/filemap.h
@@ -0,0 +1,13 @@
+#ifndef _TRACE_FILEMAP_H
+#define _TRACE_FILEMAP_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_TRACE(filemap_add_to_page_cache,
+	TPPROTO(struct address_space *mapping, pgoff_t offset),
+	TPARGS(mapping, offset));
+DECLARE_TRACE(filemap_remove_from_page_cache,
+	TPPROTO(struct address_space *mapping, pgoff_t offset),
+	TPARGS(mapping, offset));
+
+#endif
diff --git a/mm/filemap.c b/mm/filemap.c
index 23acefe..23f75d2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -34,6 +34,7 @@
 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
 #include <linux/memcontrol.h>
 #include <linux/mm_inline.h> /* for page_is_file_cache() */
+#include <trace/filemap.h>
 #include "internal.h"
 
 /*
@@ -43,6 +44,8 @@
 
 #include <asm/mman.h>
 
+DEFINE_TRACE(filemap_add_to_page_cache);
+DEFINE_TRACE(filemap_remove_from_page_cache);
 
 /*
  * Shared mappings implemented 30.11.1994. It's not fully working yet,
@@ -120,6 +123,7 @@ void __remove_from_page_cache(struct page *page)
 	page->mapping = NULL;
 	mapping->nrpages--;
 	__dec_zone_page_state(page, NR_FILE_PAGES);
+	trace_filemap_remove_from_page_cache(mapping, page->index);
 	BUG_ON(page_mapped(page));
 	mem_cgroup_uncharge_cache_page(page);
 
@@ -475,6 +479,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 		if (likely(!error)) {
 			mapping->nrpages++;
 			__inc_zone_page_state(page, NR_FILE_PAGES);
+			trace_filemap_add_to_page_cache(mapping, offset);
 		} else {
 			page->mapping = NULL;
 			mem_cgroup_uncharge_cache_page(page);

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