From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: * X-Spam-Status: No, score=1.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F8D8C04AB4 for ; Tue, 21 May 2019 11:24:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 65CE4216B7 for ; Tue, 21 May 2019 11:24:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558437871; bh=LPz/8bnSOocyng6G1JsrkcWmG8OLv9Hua93ZPja6LPY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=hGcVwi6neKNONE1iPwxT+LwuoHhBQr2gyrii8tQyHtTFAT89dx4/qUIzGn/Wd7e5l C9YQ4zXQTvu6VVEfMDuKep6j0FUUFIkf65wev/Jg9n6xnVqeFIkKVuE0HOp/aRGWZ6 GaUTuR4AOQYkOx8jLsFEcQHifFDPDxanjsdJrr1g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727827AbfEULYa (ORCPT ); Tue, 21 May 2019 07:24:30 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:37935 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726525AbfEULYa (ORCPT ); Tue, 21 May 2019 07:24:30 -0400 Received: by mail-pg1-f194.google.com with SMTP id j26so8448627pgl.5 for ; Tue, 21 May 2019 04:24:29 -0700 (PDT) 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-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=19lOUlmB0BXO2qy5+86EiFCLj8kI8GOhTNcbKNP7IO4=; b=S1A49C+HintLz0B+SoljY1DZ+r/eIEs4KFC28suXS3959nT/6EWXp4DI2Hc+Tlen8S vB+Qbpsv2m5qgoK8CmilOeTDl8V6y9hbS4CItRdQtUmjRDMklWE23CCYc/0peS+xw6+Y cnkJOjOcCPgHD2SboZUNH2YsKQGSFeNtzSDHGRf76hqRxwrK4u1xD2aU/DTQHelRa57l BLGQK5JNVAwyZQ0HLm4LO0V7qyiFOLynSszkeDhbIiLPW8XQO0skywk3p3ztbc7FsVAM KpukQKuW1LrrRVbM/UXWBtKLOH70x7UncQ55LJ1dMTNyuWiD2Li+Dqgxj1piX/e4sg2B hNvQ== X-Gm-Message-State: APjAAAUi/s5FKMFHDKpuEd8ryHPTOVYfUt0Pf++8RNZ9GS1Grc5EYT7n CZfGU9hpvxiNGRd/PN7fsyQ= 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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