From: Rik van Riel <riel@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>
Cc: 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>,
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 11:08:15 -0500 [thread overview]
Message-ID: <1483027695.11006.97.camel@redhat.com> (raw)
In-Reply-To: <20161220134312.17332-1-vbabka@suse.cz>
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On Tue, 2016-12-20 at 14:43 +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: Rik van Riel <riel@redhat.com>
--
All Rights Reversed.
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prev parent reply other threads:[~2016-12-29 16:08 UTC|newest]
Thread overview: 5+ 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
2016-12-20 13:43 ` Vlastimil Babka
2016-12-29 12:00 ` Mel Gorman
2016-12-29 12:00 ` Mel Gorman
2016-12-29 16:08 ` Rik van Riel [this message]
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