From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 601106B0038 for ; Tue, 26 Sep 2017 05:51:30 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id i131so11379108wma.1 for ; Tue, 26 Sep 2017 02:51:30 -0700 (PDT) Received: from outbound-smtp04.blacknight.com (outbound-smtp04.blacknight.com. [81.17.249.35]) by mx.google.com with ESMTPS id k54si488612edd.18.2017.09.26.02.51.29 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 26 Sep 2017 02:51:29 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp04.blacknight.com (Postfix) with ESMTPS id 94378F4013 for ; Tue, 26 Sep 2017 09:51:28 +0000 (UTC) Date: Tue, 26 Sep 2017 10:51:27 +0100 From: Mel Gorman Subject: Re: [RFC 0/2] Use HighAtomic against long-term fragmentation Message-ID: <20170926095127.p5ocg44et2g62gku@techsingularity.net> References: <1506415604-4310-1-git-send-email-zhuhui@xiaomi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1506415604-4310-1-git-send-email-zhuhui@xiaomi.com> Sender: owner-linux-mm@kvack.org List-ID: To: Hui Zhu 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org