From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] mm, page_alloc: convert page_group_by_mobility_disable to static key
Date: Thu, 29 Dec 2016 12:00:13 +0000 [thread overview]
Message-ID: <20161229120013.lscts45z6yec2ecg@techsingularity.net> (raw)
In-Reply-To: <20161220134312.17332-1-vbabka@suse.cz>
On Tue, Dec 20, 2016 at 02:43:12PM +0100, Vlastimil Babka wrote:
> The flag is rarely enabled or even changed, so it's an ideal static key
> candidate. Since it's being checked in the page allocator fastpath via
> gfpflags_to_migratetype(), it may actually save some valuable cycles.
>
> Here's a diff excerpt from __alloc_pages_nodemask() assembly:
>
> -movl page_group_by_mobility_disabled(%rip), %ecx
> +.byte 0x0f,0x1f,0x44,0x00,0
> movl %r9d, %eax
> shrl $3, %eax
> andl $3, %eax
> -testl %ecx, %ecx
> -movl $0, %ecx
> -cmovne %ecx, %eax
>
> I.e. a NOP instead of test, conditional move and some assisting moves.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
--
Mel Gorman
SUSE Labs
--
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/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-12-29 12:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-20 13:43 [PATCH] mm, page_alloc: convert page_group_by_mobility_disable to static key Vlastimil Babka
2016-12-29 12:00 ` Mel Gorman [this message]
2016-12-29 16:08 ` Rik van Riel
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=20161229120013.lscts45z6yec2ecg@techsingularity.net \
--to=mgorman@techsingularity.net \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
--cc=vbabka@suse.cz \
/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;
as well as URLs for NNTP newsgroup(s).