From: Nick Piggin <npiggin@kernel.dk>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@kernel.dk>
Subject: Re: [RFC][PATCH 05/10] mm: Remove likely() from grab_cache_page_write_begin()
Date: Tue, 7 Dec 2010 17:56:59 +1100 [thread overview]
Message-ID: <20101207065659.GA3307@amd> (raw)
In-Reply-To: <1291688650.16223.124.camel@gandalf.stny.rr.com>
On Mon, Dec 06, 2010 at 09:24:10PM -0500, Steven Rostedt wrote:
> [ Resending to Nick's real email address ]
>
> From: Steven Rostedt <srostedt@redhat.com>
>
> Running the annotated branch profiler on a box doing average work
> (firefox, evolution, xchat, distcc farm), the likely() used in
> grab_cache_page_write_begin() was incorrect most of the time:
>
> correct incorrect % Function File Line
> ------- --------- - -------- ---- ----
> 1924262 71332401 97 grab_cache_page_write_begin filemap.c 2206
>
> Adding a trace_printk() and running the function tracer limited to
> just this function I can see:
>
> gconfd-2-2696 [000] 4467.268935: grab_cache_page_write_begin: page= (null) mapping=ffff8800676a9460 index=7
> gconfd-2-2696 [000] 4467.268946: grab_cache_page_write_begin <-ext3_write_begin
> gconfd-2-2696 [000] 4467.268947: grab_cache_page_write_begin: page= (null) mapping=ffff8800676a9460 index=8
> gconfd-2-2696 [000] 4467.268959: grab_cache_page_write_begin <-ext3_write_begin
> gconfd-2-2696 [000] 4467.268960: grab_cache_page_write_begin: page= (null) mapping=ffff8800676a9460 index=9
> gconfd-2-2696 [000] 4467.268972: grab_cache_page_write_begin <-ext3_write_begin
> gconfd-2-2696 [000] 4467.268973: grab_cache_page_write_begin: page= (null) mapping=ffff8800676a9460 index=10
> gconfd-2-2696 [000] 4467.268991: grab_cache_page_write_begin <-ext3_write_begin
> gconfd-2-2696 [000] 4467.268992: grab_cache_page_write_begin: page= (null) mapping=ffff8800676a9460 index=11
> gconfd-2-2696 [000] 4467.269005: grab_cache_page_write_begin <-ext3_write_begin
>
> Which shows that a lot of calls from ext3_write_begin will result in
> the page returned by "find_lock_page" will be NULL.
>
> Cc: Nick Piggin <npiggin@kernel.dk>
Looks good,
Acked-by: Nick Piggin <npiggin@kernel.dk>
next prev parent reply other threads:[~2010-12-07 6:57 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-07 1:58 [RFC][PATCH 00/10] incorrect unlikely() and likely() cleanups Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 01/10] sched: Change rt_task(prev) in pre_schedule_rt to likely Steven Rostedt
2010-12-07 3:25 ` Yong Zhang
2010-12-07 3:32 ` Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 02/10] mm: Remove likely() from mapping_unevictable() Steven Rostedt
2010-12-07 2:22 ` Steven Rostedt
2010-12-07 7:02 ` Nick Piggin
2010-12-07 13:06 ` Steven Rostedt
2010-12-07 16:26 ` Rik van Riel
2010-12-10 7:00 ` KOSAKI Motohiro
2010-12-10 7:06 ` Joe Perches
2010-12-10 8:08 ` Miles Bader
2010-12-11 0:09 ` Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 03/10] workqueue: It is likely that WORKER_NOT_RUNNING is true Steven Rostedt
2010-12-07 9:49 ` Tejun Heo
2010-12-07 13:07 ` Steven Rostedt
2010-12-11 0:08 ` Steven Rostedt
2010-12-11 0:09 ` Tejun Heo
2010-12-11 0:12 ` Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 04/10] sched: Change pick_next_task_rt from unlikely to likely Steven Rostedt
2010-12-07 2:46 ` Gregory Haskins
2010-12-07 2:59 ` Steven Rostedt
2010-12-11 0:07 ` Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 05/10] mm: Remove likely() from grab_cache_page_write_begin() Steven Rostedt
2010-12-07 2:24 ` Steven Rostedt
2010-12-07 6:56 ` Nick Piggin [this message]
2010-12-07 1:58 ` [RFC][PATCH 06/10] sched: Remove unlikely() from rt_policy() in sched.c Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 07/10] x86: Remove unlikey()s from sched_switch segment tests Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 08/10] fs: Remove unlikely() from fput_light() Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 09/10] fs: Remove unlikely() from fget_light() Steven Rostedt
2010-12-07 1:58 ` [RFC][PATCH 10/10] sched: Remove unlikely() from ttwu_post_activation Steven Rostedt
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