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[209.85.220.65]) by mx.google.com with SMTPS id z134sor20299666pgz.86.2019.05.21.04.24.29 for (Google Transport Security); Tue, 21 May 2019 04:24:29 -0700 (PDT) Received-SPF: pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=P6sVSJ8V; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=19lOUlmB0BXO2qy5+86EiFCLj8kI8GOhTNcbKNP7IO4=; b=P6sVSJ8VYNp1+Lx4Dxzurk25CX9vkVoXH08GrauyQziSWr+fupC7M+k6u4UTyrGsbY jBDI1AiX+THg04/RNegnkFskFWc2Hde+r/6tC2DP+zcvIs4X2lQyrOQ2m6quf3I3IrDK 7n5vzbRA0a6/LqCBIQsIMR/vnOEKPgxN7hl3hjGnf6LP0JrsutNyi9WSvdtj+Jw6mZQG MwxVmfse/1ttaoz24+lxlrWvFBtGZK+tuT51jRdv/4s+Uwa881cOKdhgis/0g1V47XZI RbKI0PyKuB5zZ1JKkzFhG9SfJxo2OfzwDIt009bJF5uw3P2FiSKwodIxOuirOUnvDbcO A2aw== X-Google-Smtp-Source: APXvYqzO8k/cpniPZ4As3COPVMn1h85852mwAsWD2KOvHeEb0TcpcFBsTAgm3gjNSBmuXcimHbfaBA== X-Received: by 2002:a63:1657:: with SMTP id 23mr30125895pgw.98.1558437869394; Tue, 21 May 2019 04:24:29 -0700 (PDT) Received: from google.com ([2401:fa00:d:0:98f1:8b3d:1f37:3e8]) by smtp.gmail.com with ESMTPSA id k13sm17361700pgr.90.2019.05.21.04.24.25 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 21 May 2019 04:24:28 -0700 (PDT) Date: Tue, 21 May 2019 20:24:23 +0900 From: Minchan Kim To: Michal Hocko Cc: Oleksandr Natalenko , Andrew Morton , LKML , linux-mm , Johannes Weiner , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , Brian Geffon Subject: Re: [RFC 4/7] mm: factor out madvise's core functionality Message-ID: <20190521112423.GH219653@google.com> References: <20190520035254.57579-1-minchan@kernel.org> <20190520035254.57579-5-minchan@kernel.org> <20190520142633.x5d27gk454qruc4o@butterfly.localdomain> <20190521012649.GE10039@google.com> <20190521063628.x2npirvs75jxjilx@butterfly.localdomain> <20190521065000.GH32329@dhcp22.suse.cz> <20190521070638.yhn3w4lpohwcqbl3@butterfly.localdomain> <20190521105256.GF219653@google.com> <20190521110030.GR32329@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521110030.GR32329@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) 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: Archived-At: List-Archive: List-Post: On Tue, May 21, 2019 at 01:00:30PM +0200, Michal Hocko wrote: > On Tue 21-05-19 19:52:56, Minchan Kim wrote: > > On Tue, May 21, 2019 at 09:06:38AM +0200, Oleksandr Natalenko wrote: > > > Hi. > > > > > > On Tue, May 21, 2019 at 08:50:00AM +0200, Michal Hocko wrote: > > > > On Tue 21-05-19 08:36:28, Oleksandr Natalenko wrote: > > > > [...] > > > > > Regarding restricting the hints, I'm definitely interested in having > > > > > remote MADV_MERGEABLE/MADV_UNMERGEABLE. But, OTOH, doing it via remote > > > > > madvise() introduces another issue with traversing remote VMAs reliably. > > > > > IIUC, one can do this via userspace by parsing [s]maps file only, which > > > > > is not very consistent, and once some range is parsed, and then it is > > > > > immediately gone, a wrong hint will be sent. > > > > > > > > > > Isn't this a problem we should worry about? > > > > > > > > See http://lkml.kernel.org/r/20190520091829.GY6836@dhcp22.suse.cz > > > > > > Oh, thanks for the pointer. > > > > > > Indeed, for my specific task with remote KSM I'd go with map_files > > > instead. This doesn't solve the task completely in case of traversal > > > through all the VMAs in one pass, but makes it easier comparing to a > > > remote syscall. > > > > I'm wondering how map_files can solve your concern exactly if you have > > a concern about the race of vma unmap/remap even there are anonymous > > vma which map_files doesn't support. > > See http://lkml.kernel.org/r/20190521105503.GQ32329@dhcp22.suse.cz Question is how it works for anonymous vma which don't have backing file. > > -- > Michal Hocko > SUSE Labs