From: Steven Rostedt <rostedt@goodmis.org>
To: Pekka Enberg <penberg@kernel.org>
Cc: Minchan Kim <minchan.kim@gmail.com>,
Theodore Ts'o <tytso@mit.edu>,
Christoph Lameter <cl@linux-foundation.org>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Matt Mackall <mpm@selenic.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
David Rientjes <rientjes@google.com>,
npiggin@kernel.dk
Subject: Re: Should we be using unlikely() around tests of GFP_ZERO?
Date: Mon, 03 Jan 2011 09:26:36 -0500 [thread overview]
Message-ID: <1294064796.3948.12.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <AANLkTik9VodSjNnubf4Psbb9TgOEufw0m2q1_e5+X165@mail.gmail.com>
On Mon, 2011-01-03 at 16:10 +0200, Pekka Enberg wrote:
> > correct incorrect % Function File Line
> > ------- --------- - -------- ---- ----
> > 6890998 2784830 28 slab_alloc slub.c 1719
> >
> > That's incorrect 28% of the time.
>
> Thanks! AFAICT, that number is high enough to justify removing the
> unlikely() annotations, no?
Personally, I think anything that is incorrect more that 5% of the time
should not have any annotation.
My rule is to use the annotation when a branch goes one way 95% or more.
With the exception of times when we want a particular path to be the
faster path, because we know its in a more critical position (as there
are cases in the scheduler and the tracing infrastructure itself).
But here, I think removing it is the right decision.
-- Steve
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next prev parent reply other threads:[~2011-01-03 14:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-02 23:48 Theodore Ts'o
2011-01-03 3:46 ` Minchan Kim
2011-01-03 7:40 ` Pekka Enberg
2011-01-03 13:45 ` Steven Rostedt
2011-01-03 14:10 ` Pekka Enberg
2011-01-03 14:26 ` Steven Rostedt [this message]
2011-01-03 13:58 ` Ted Ts'o
2011-01-03 14:09 ` Pekka Enberg
2011-01-03 17:23 ` Matt Mackall
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