From: Pekka Enberg <penberg@kernel.org>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: 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,
Steven Rostedt <rostedt@goodmis.org>,
David Rientjes <rientjes@google.com>,
npiggin@kernel.dk
Subject: Re: Should we be using unlikely() around tests of GFP_ZERO?
Date: Mon, 3 Jan 2011 09:40:57 +0200 [thread overview]
Message-ID: <AANLkTinz52Ky5BhU-gHq8vx9=1uoN+iuDn1f0C8fnSjQ@mail.gmail.com> (raw)
In-Reply-To: <AANLkTi=9ZNk6w8PxvveWHy5+okfTyKUj3L2ywFOuFjoq@mail.gmail.com>
Hi,
On Mon, Jan 3, 2011 at 8:48 AM, Theodore Ts'o <tytso@mit.edu> wrote:
>> Given the patches being busily submitted by trivial patch submitters to
>> make use kmem_cache_zalloc(), et. al, I believe we should remove the
>> unlikely() tests around the (gfp_flags & __GFP_ZERO) tests, such as:
>>
>> - if (unlikely((flags & __GFP_ZERO) && objp))
>> + if ((flags & __GFP_ZERO) && objp)
>> memset(objp, 0, obj_size(cachep));
>>
>> Agreed? If so, I'll send a patch...
On Mon, Jan 3, 2011 at 5:46 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
> I support it.
I guess the rationale here is that if you're going to take the hit of
memset() you can take the hit of unlikely() as well. We're optimizing
for hot call-sites that allocate a small amount of memory and
initialize everything themselves. That said, I don't think the
unlikely() annotation matters much either way and am for removing it
unless people object to that.
On Mon, Jan 3, 2011 at 5:46 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
> Recently Steven tried to gather the information.
> http://thread.gmane.org/gmane.linux.kernel/1072767
> Maybe he might have a number for that.
That would be interesting, sure.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-01-03 7:41 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 [this message]
2011-01-03 13:45 ` Steven Rostedt
2011-01-03 14:10 ` Pekka Enberg
2011-01-03 14:26 ` Steven Rostedt
2011-01-03 13:58 ` Ted Ts'o
2011-01-03 14:09 ` Pekka Enberg
2011-01-03 17:23 ` Matt Mackall
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='AANLkTinz52Ky5BhU-gHq8vx9=1uoN+iuDn1f0C8fnSjQ@mail.gmail.com' \
--to=penberg@kernel.org \
--cc=cl@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=minchan.kim@gmail.com \
--cc=mpm@selenic.com \
--cc=npiggin@kernel.dk \
--cc=penberg@cs.helsinki.fi \
--cc=rientjes@google.com \
--cc=rostedt@goodmis.org \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox