From: Mel Gorman <mgorman@techsingularity.net>
To: zbestahu@aliyun.com
Cc: akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com,
hannes@cmpxchg.org, minchan@kernel.org, linux-mm@kvack.org,
Yue Hu <huyue2@coolpad.com>
Subject: Re: [PATCH] mm/page_alloc.c: improve allocation fast path
Date: Sat, 8 Jul 2017 20:47:39 +0100 [thread overview]
Message-ID: <20170708194739.chisy47mz4c2c2ye@techsingularity.net> (raw)
In-Reply-To: <1499477319-1395-1-git-send-email-zbestahu@aliyun.com>
On Sat, Jul 08, 2017 at 09:28:39AM +0800, zbestahu@aliyun.com wrote:
> From: Yue Hu <huyue2@coolpad.com>
>
> We currently is taking time to check if the watermark is safe when
> alloc_flags is setting with ALLOC_NO_WATERMARK in slowpath, the check
> to alloc_flags is faster check which should be first check option
> compared to the slow check of watermark, it could benefit to urgency
> allocation request in slowpath, it also almost has no effect for
> allocation with successful watermark check.
>
> Signed-off-by: Yue Hu <huyue2@coolpad.com>
NAK. Was this measured as being a benefit to anything?
ALLOC_NO_WATERMARKS is rare so it's in the slow path. Even though the
watermark check is redundent when watermarks should be ignored, your patch
adds a branch that is rarely true to the common case. The comment you move
even gives a hint as to why it's located there!
--
Mel Gorman
SUSE Labs
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prev parent reply other threads:[~2017-07-08 19:47 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-08 1:28 zbestahu
2017-07-08 19:47 ` Mel Gorman [this message]
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