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[2a02:6b8:0:1619::183]) by mx.google.com with ESMTPS id x18si13022038lfc.83.2019.05.28.01.58.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 May 2019 01:58:51 -0700 (PDT) Received-SPF: pass (google.com: domain of khlebnikov@yandex-team.ru designates 2a02:6b8:0:1619::183 as permitted sender) client-ip=2a02:6b8:0:1619::183; Authentication-Results: mx.google.com; dkim=pass header.i=@yandex-team.ru header.s=default header.b=u3veDeuD; spf=pass (google.com: domain of khlebnikov@yandex-team.ru designates 2a02:6b8:0:1619::183 as permitted sender) smtp.mailfrom=khlebnikov@yandex-team.ru; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=yandex-team.ru Received: from mxbackcorp1j.mail.yandex.net (mxbackcorp1j.mail.yandex.net [IPv6:2a02:6b8:0:1619::162]) by forwardcorp1j.mail.yandex.net (Yandex) with ESMTP id 820A62E0A7B; Tue, 28 May 2019 11:58:50 +0300 (MSK) Received: from smtpcorp1j.mail.yandex.net (smtpcorp1j.mail.yandex.net [2a02:6b8:0:1619::137]) by mxbackcorp1j.mail.yandex.net (nwsmtp/Yandex) with ESMTP id uDbd8mNgjG-wnp8YhTV; Tue, 28 May 2019 11:58:50 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1559033930; bh=e67vXEFlguLHoPzm4i6XNcC1TsQ4C+poa1KdWpDWoFM=; h=In-Reply-To:Message-ID:From:Date:References:To:Subject:Cc; b=u3veDeuDUQqhxqZN/gx25dJHfV9rTVsyH55dJyggW9tsHn9L8tEWLJMbVDXtSNkn+ /Mu+KdcC/MNOuZx0EXTTo9HeqV7S1epVvwf7ngTgKEAJdcLz0aKJuK6/qOcof9TqCc 5C72JSfB2X5Dg3IePfeIr7t3TMMHRgLn5I8OXHEs= Authentication-Results: mxbackcorp1j.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-red.dhcp.yndx.net (dynamic-red.dhcp.yndx.net [2a02:6b8:0:40c:d877:17c:81de:6e43]) by smtpcorp1j.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id 56Lg4wTzc1-wn8qqC4T; Tue, 28 May 2019 11:58:49 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: Re: [PATCH RFC] mm/madvise: implement MADV_STOCKPILE (kswapd from user space) To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vladimir Davydov , Johannes Weiner , Tejun Heo , Andrew Morton , Mel Gorman , Roman Gushchin , linux-api@vger.kernel.org References: <155895155861.2824.318013775811596173.stgit@buzz> <20190527141223.GD1658@dhcp22.suse.cz> <20190527142156.GE1658@dhcp22.suse.cz> <20190527143926.GF1658@dhcp22.suse.cz> <9c55a343-2a91-46c6-166d-41b94bf5e9c8@yandex-team.ru> <20190528065153.GB1803@dhcp22.suse.cz> <20190528073835.GP1658@dhcp22.suse.cz> <5af1ba69-61d1-1472-4aa3-20beb4ae44ae@yandex-team.ru> <20190528084243.GT1658@dhcp22.suse.cz> From: Konstantin Khlebnikov Message-ID: <4ecf491b-68b5-9a65-5074-648a4f94d2b0@yandex-team.ru> Date: Tue, 28 May 2019 11:58:49 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190528084243.GT1658@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 28.05.2019 11:42, Michal Hocko wrote: > On Tue 28-05-19 11:04:46, Konstantin Khlebnikov wrote: >> On 28.05.2019 10:38, Michal Hocko wrote: > [...] >>> Could you define the exact semantic? Ideally something for the manual >>> page please? >>> >> >> Like kswapd which works with thresholds of free memory this one reclaims >> until 'free' (i.e. memory which could be allocated without invoking >> direct recliam of any kind) is lower than passed 'size' argument. > > s@lower@higher@ I guess Yep. My wording still bad. 'size' argument should be called 'watermark' or 'threshold'. I.e. reclaim while 'free' memory is lower passed 'threshold'. > >> Thus right after madvise(NULL, size, MADV_STOCKPILE) 'size' bytes >> could be allocated in this memory cgroup without extra latency from >> reclaimer if there is no other memory consumers. >> >> Reclaimed memory is simply put into free lists in common buddy allocator, >> there is no reserves for particular task or cgroup. >> >> If overall memory allocation rate is smooth without rough spikes then >> calling MADV_STOCKPILE in loop periodically provides enough room for >> allocations and eliminates direct reclaim from all other tasks. >> As a result this eliminates unpredictable delays caused by >> direct reclaim in random places. > > OK, this makes it more clear to me. Thanks for the clarification! > I have clearly misunderstood and misinterpreted target as the reclaim > target rather than free memory target. Sorry about the confusion. > I sill think that this looks like an abuse of the madvise but if there > is a wider consensus this is acceptable I will not stand in the way. >