From: Mel Gorman <mgorman@techsingularity.net>
To: Hui Zhu <zhuhui@xiaomi.com>
Cc: akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz,
hillf.zj@alibaba-inc.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, teawater@gmail.com
Subject: Re: [RFC 0/2] Use HighAtomic against long-term fragmentation
Date: Tue, 26 Sep 2017 10:51:27 +0100 [thread overview]
Message-ID: <20170926095127.p5ocg44et2g62gku@techsingularity.net> (raw)
In-Reply-To: <1506415604-4310-1-git-send-email-zhuhui@xiaomi.com>
On Tue, Sep 26, 2017 at 04:46:42PM +0800, Hui Zhu wrote:
> Current HighAtomic just to handle the high atomic page alloc.
> But I found that use it handle the normal unmovable continuous page
> alloc will help to against long-term fragmentation.
>
This is not wise. High-order atomic allocations do not always have a
smooth recovery path such as network drivers with large MTUs that have no
choice but to drop the traffic and hope for a retransmit. That's why they
have the highatomic reserve. If the reserve is used for normal unmovable
allocations then allocation requests that could have waited for reclaim
may cause high-order atomic allocations to fail. Changing it may allow
improve latencies in some limited cases while causing functional failures
in others. If there is a special case where there are a large number of
other high-order allocations then I would suggest increasing min_free_kbytes
instead as a workaround.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2017-09-26 9:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-26 8:46 Hui Zhu
2017-09-26 8:46 ` [RFC 1/2] Try to use HighAtomic if try to alloc umovable page that order is not 0 Hui Zhu
2017-09-26 10:47 ` Michal Hocko
2017-09-26 8:46 ` [RFC 2/2] Change limit of HighAtomic from 1% to 10% Hui Zhu
2017-09-26 9:51 ` Mel Gorman [this message]
2017-09-26 10:04 ` [RFC 0/2] Use HighAtomic against long-term fragmentation Hui Zhu
2017-09-26 10:43 ` Mel Gorman
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