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
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WARNING: multiple messages have this Message-ID (diff)
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
next prev parent reply other threads:[~2016-12-29 12:00 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 [this message]
2016-12-29 12:00 ` Mel Gorman
2016-12-29 16:08 ` Rik van Riel
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