From: Vlastimil Babka <vbabka@suse.cz>
To: Xishi Qiu <qiuxishi@huawei.com>, "mel@csn.ul.ie" <mel@csn.ul.ie>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <js1304@gmail.com>,
Mel Gorman <mgorman@techsingularity.net>
Cc: Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: mm/compact: why use low watermark to determine whether compact is finished instead of use high watermark?
Date: Fri, 22 Jul 2016 11:04:20 +0200 [thread overview]
Message-ID: <0b580155-d99a-f4a4-ef76-6166b41180aa@suse.cz> (raw)
In-Reply-To: <5791DFD4.5080207@huawei.com>
On 07/22/2016 10:56 AM, Xishi Qiu wrote:
> Hi,
>
> I find all the watermarks in mm/compaction.c are low_wmark_pages(),
> so why not use high watermark to determine whether compact is finished?
Why would you use high watermark? Quite the opposite, I want to move
towards min watermark (precisely, the one in alloc_flags which is
usually min) in this series:
https://lkml.org/lkml/2016/6/24/222
especially:
https://lkml.org/lkml/2016/6/24/214
> e.g.
> __alloc_pages_nodemask()
> get_page_from_freelist()
> this is fast path, use use low_wmark_pages() in __zone_watermark_ok()
>
> __alloc_pages_slowpath()
> this is slow path, usually use min_wmark_pages()
Yes, and compaction should be finished when allocation can succeed, so
match __alloc_pages_slowpath().
>
> kswapd
> balance_pgdat()
> use high_wmark_pages() to determine whether zone is balanced
>
> Thanks,
> Xishi Qiu
>
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next prev parent reply other threads:[~2016-07-22 9:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-22 8:56 Xishi Qiu
2016-07-22 9:04 ` Vlastimil Babka [this message]
2016-07-22 9:21 ` Xishi Qiu
2016-07-22 9:30 ` Vlastimil Babka
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