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[209.85.220.65]) by mx.google.com with SMTPS id g1sor21550816pgr.2.2019.05.21.08.33.13 for (Google Transport Security); Tue, 21 May 2019 08:33:13 -0700 (PDT) Received-SPF: pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@cmpxchg-org.20150623.gappssmtp.com header.s=20150623 header.b=rnqXgMMh; spf=pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=cmpxchg.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=8JdJVvAGyNC8PSXsjfUN8u+zmKF1hLoAAqIvD329Mjs=; b=rnqXgMMhyVETxYuovuKic/EJW9jX8R4OBSqbR8Ns4TCHRCgBy8Sb1k0zAYZ59/J94S 6Iy/Sm1itRyXny9cYzoIGNEtsR/bRvQoGUIh852eQWPsq5aGavHDwD0W6w2MpswU3Coc y5ymxRJjWQkhYAf0ob40InCjHd1X+a9yIvvmOF7KY43VbWNgKA5IAyDiqwOLKg6lUoqL 77/P03tIKEXYXyvDAoD5fDljlvUS67qiJRndivR1QEvDomd3Shrbs0vyHhTytRp2wLB5 JUozEO+U/NShOuhdDwTC0JpBQoX+2f8Vk6Ht9mI5S7oyQrykqElGO8iOhesf6Ir1faQS V5OQ== X-Google-Smtp-Source: APXvYqwlng0s4LJPDKCEGz+dJqb/FMYHQKwaVN6ia1yxZapGNrVbL/8WU/wAPFu2zQ4PE5OMy57Bpw== X-Received: by 2002:a63:d901:: with SMTP id r1mr45310557pgg.271.1558452793234; Tue, 21 May 2019 08:33:13 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::2:5a76]) by smtp.gmail.com with ESMTPSA id 135sm38967196pfb.97.2019.05.21.08.33.11 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 21 May 2019 08:33:12 -0700 (PDT) Date: Tue, 21 May 2019 11:33:10 -0400 From: Johannes Weiner To: Minchan Kim Cc: Michal Hocko , Andrew Morton , LKML , linux-mm , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , Brian Geffon , linux-api@vger.kernel.org Subject: Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER Message-ID: <20190521153310.GA3218@cmpxchg.org> References: <20190520035254.57579-1-minchan@kernel.org> <20190520035254.57579-8-minchan@kernel.org> <20190520092801.GA6836@dhcp22.suse.cz> <20190521025533.GH10039@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521025533.GH10039@google.com> User-Agent: Mutt/1.11.4 (2019-03-13) 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 Tue, May 21, 2019 at 11:55:33AM +0900, Minchan Kim wrote: > On Mon, May 20, 2019 at 11:28:01AM +0200, Michal Hocko wrote: > > [cc linux-api] > > > > On Mon 20-05-19 12:52:54, Minchan Kim wrote: > > > System could have much faster swap device like zRAM. In that case, swapping > > > is extremely cheaper than file-IO on the low-end storage. > > > In this configuration, userspace could handle different strategy for each > > > kinds of vma. IOW, they want to reclaim anonymous pages by MADV_COLD > > > while it keeps file-backed pages in inactive LRU by MADV_COOL because > > > file IO is more expensive in this case so want to keep them in memory > > > until memory pressure happens. > > > > > > To support such strategy easier, this patch introduces > > > MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER options in madvise(2) like > > > that /proc//clear_refs already has supported same filters. > > > They are filters could be Ored with other existing hints using top two bits > > > of (int behavior). > > > > madvise operates on top of ranges and it is quite trivial to do the > > filtering from the userspace so why do we need any additional filtering? > > > > > Once either of them is set, the hint could affect only the interested vma > > > either anonymous or file-backed. > > > > > > With that, user could call a process_madvise syscall simply with a entire > > > range(0x0 - 0xFFFFFFFFFFFFFFFF) but either of MADV_ANONYMOUS_FILTER and > > > MADV_FILE_FILTER so there is no need to call the syscall range by range. > > > > OK, so here is the reason you want that. The immediate question is why > > cannot the monitor do the filtering from the userspace. Slightly more > > work, all right, but less of an API to expose and that itself is a > > strong argument against. > > What I should do if we don't have such filter option is to enumerate all of > vma via /proc//maps and then parse every ranges and inode from string, > which would be painful for 2000+ vmas. Just out of curiosity, how do you get to 2000+ distinct memory regions in the address space of a mobile app? I'm assuming these aren't files, but rather anon objects with poor grouping. Is that from guard pages between individual heap allocations or something?