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[209.85.220.65]) by mx.google.com with SMTPS id i21sor20924698pgl.11.2019.05.21.03.53.02 for (Google Transport Security); Tue, 21 May 2019 03:53:03 -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=kqar2URp; 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=2Sic2O7wb52L5CR9NZn4I8czhdSoXaChDb/juZvSzjk=; b=kqar2URpzHjwHZxhz9FhJySyjNcvp48Yvzwkmxf2VubqeURESj6Vff0i/jsIthS7y9 fPRjulw8tqg5W/oB23bfQ6UFnd8nscb2aa5s8AAzR6x2gUQbSsbmCcBbB7K1Uh/hzbiv ZeoxCNKSzYQ80A1lxxKgGkbjkN61+GLe0vQUUtixqAl/tDRPbShOiB0e1oWE/ejNmBFv dqBUvs9CRSKIAN4+yxm1aYazKW+oNgGlzkPpuhdWb4Z3w7wGKiYDfQlj3WlYFi/as9VJ VFMSyRQc0lXkd32xUqS1qV7HC6vxnJFGeLEI1qV1TDkfxSHCiLUZ0ohK/bMC56iKFykQ 9XTA== X-Google-Smtp-Source: APXvYqzWwsWL/43VXabxfdXeVLd95/lm6etnN5YVFlIWX66F8XbYX0NSYXLCPcewwlk31OvvzN3rhw== X-Received: by 2002:a63:ba5a:: with SMTP id l26mr80865856pgu.183.1558435982668; Tue, 21 May 2019 03:53:02 -0700 (PDT) Received: from google.com ([2401:fa00:d:0:98f1:8b3d:1f37:3e8]) by smtp.gmail.com with ESMTPSA id j64sm37602676pfb.126.2019.05.21.03.52.58 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 21 May 2019 03:53:01 -0700 (PDT) Date: Tue, 21 May 2019 19:52:56 +0900 From: Minchan Kim To: Oleksandr Natalenko Cc: Michal Hocko , 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: <20190521105256.GF219653@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521070638.yhn3w4lpohwcqbl3@butterfly.localdomain> 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: 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. > > -- > Best regards, > Oleksandr Natalenko (post-factum) > Senior Software Maintenance Engineer