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=-0.8 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_SANE_1 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 B7A0DC2D0CE for ; Tue, 21 Jan 2020 18:43:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D0CF24655 for ; Tue, 21 Jan 2020 18:43:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579632214; bh=PFfpAVd2TNsL/dheeDPli6fd1fy1Nwnh7wO20FPeP9M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=j8n151G7+hIcaNpuScMI5BuAH5xuDZuO1ukkAuyQTkLgUtxke835cHozTRrH+Vg4k jfjP5/V+Ulwrnhjt2YBCZ8gSN+KOUeTiBFphFCL3EZbbC5HYXG4Uebe7+xdbMNXX22 +DxudC/u/nvJQflUrk1FLUSf0d2nDdccvSkOq/SY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729335AbgAUSnd (ORCPT ); Tue, 21 Jan 2020 13:43:33 -0500 Received: from mail-pf1-f196.google.com ([209.85.210.196]:41195 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728186AbgAUSnd (ORCPT ); Tue, 21 Jan 2020 13:43:33 -0500 Received: by mail-pf1-f196.google.com with SMTP id w62so1929816pfw.8; Tue, 21 Jan 2020 10:43:33 -0800 (PST) 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=TJ+7aT9JrT35zrniT4wJhBHLpa2gWNRqolwPFRdXNl8=; b=qwnADoKDat/YhCRnaZl4Dg02qquO4O5tRj7h87WizvuQzcgFVEzYdaUmyepd5QxIGU 14bhP/TmITwP/o1pyJ6r+hYcpYMfm/O/HFpxkhcF8ERmQ91rIyCuMNDipDC/jdc5dgX6 fzywdiU6BqqEwQ8FKxgqsveg3J+FC1PyqeWWnh9Cb3poznc9hbOffB8YTjWuVB19U6Hl 6qBAMnwRE195EBDUaU9B/0sQbzket/zlXZ62HceirL41G2aioBLTjWkQ1gyqsw7ZJTlX FW3djklbwl4sIF6g71klJZsJw5pQtEGEC19z1LyvoB6814XyAFviTq8lHnIqowW3n4L7 ho6Q== 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=TJ+7aT9JrT35zrniT4wJhBHLpa2gWNRqolwPFRdXNl8=; b=MElUNuy7wD/9MVvBsQwSlerHLeaPJKY1TlbxixJ8H7X+rNlbp9tpBvVim3ANdMjmV1 fWMbCMAQi2PysEq/Sk0L2BN0b/Z6VLaz+tO+uGRMdnxgeao5Sdpk323iKHDxjnmY/6Kz KwL92d3h1HvS+rm15xGf8UaCB/wa46oIW8W4F6NY630vnJmpfSDfOa1KONcpA1PHmefn +E4W3VobtS5k6SEYFuUF6FFdZvjUxq7QrW880YiQJizSprr7vKeTT1htIVp8U5JHLLLo FDOcLB40trkEISxP5sHSG71MR24hcr9sMeuSEOeExL7nP0A8+59yZoWgzScysxYUvUEN 4Wdg== X-Gm-Message-State: APjAAAXAYP0YaZwLAnrhsFZ0mqQkFTjXva004PzwqjzIU8kUMihpl0Qn SXHoc+3os6JkUYgcNM+izeY= X-Google-Smtp-Source: APXvYqy6RfD+/6cAJ0+WEpdhy0U/Bt3izVp6T3pODtKsa6rEmIHQdIGbDEjrEZgYJ8KJBrXDBtFceA== X-Received: by 2002:aa7:864a:: with SMTP id a10mr5913530pfo.233.1579632212761; Tue, 21 Jan 2020 10:43:32 -0800 (PST) Received: from google.com ([2620:15c:211:1:3e01:2939:5992:52da]) by smtp.gmail.com with ESMTPSA id o7sm46611619pfg.138.2020.01.21.10.43.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jan 2020 10:43:31 -0800 (PST) Date: Tue, 21 Jan 2020 10:43:29 -0800 From: Minchan Kim To: Michal Hocko Cc: "Kirill A. Shutemov" , Kirill Tkhai , Andrew Morton , LKML , linux-mm , linux-api@vger.kernel.org, oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Johannes Weiner , Shakeel Butt , John Dias , christian.brauner@ubuntu.com, sjpark@amazon.de Subject: Re: [PATCH v2 2/5] mm: introduce external memory hinting API Message-ID: <20200121184329.GG140922@google.com> References: <20200116235953.163318-1-minchan@kernel.org> <20200116235953.163318-3-minchan@kernel.org> <20200117115225.GV19428@dhcp22.suse.cz> <20200120112722.GY18451@dhcp22.suse.cz> <20200120123935.onlls7enjtzenbvt@box> <20200120132405.GF18451@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200120132405.GF18451@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 Mon, Jan 20, 2020 at 02:24:05PM +0100, Michal Hocko wrote: > On Mon 20-01-20 15:39:35, Kirill A. Shutemov wrote: > > On Mon, Jan 20, 2020 at 12:27:22PM +0100, Michal Hocko wrote: > > > On Mon 20-01-20 13:24:35, Kirill Tkhai wrote: > [...] > > > > Even two threads on common memory need a synchronization > > > > to manage mappings in a sane way. Managing memory from two processes > > > > is the same in principle, and the only difference is that another level > > > > of synchronization is required. > > > > > > Well, not really. The operation might simply attempt to perform an > > > operation on a specific memory area and get a failure if it doesn't > > > reference the same object anymore. What I think we need is some form of > > > a handle to operate on. In the past we have discussed several > > > directions. I was proposing /proc/self/map_anon/ (analogous to > > > map_files) where you could inspect anonymous memory and get a file > > > handle for it. madvise would then operate on the fd and then there > > > shouldn't be a real problem to revalidate that the object is still > > > valid. But there was no general enthusiasm about that approach. There > > > are likely some land mines on the way. > > > > Converting anon memory to file-backed is bad idea and going to backfire. > > I didn't mean to convert. I meant to expose that information via proc > the same way we do for file backed mappings. That shouldn't really > require to re-design the way how anonymous vma work IMO. But I haven't > tried that so there might be many gotchas there. > > There are obvious things to think about though. Such fd cannot be sent > to other processes (SCM stuff), mmap of the file would have to be > disallowed and many others I am not aware of. I am not even pushing this > direction because I am not convinced about how viable it is myself. But > it would sound like a nice extension of the existing mechanism we have > and a file based madvise sounds attractive to me as well because we > already have that. I am not a fan of fd based approach but I already reserved last argument of the API as extendable field so we could use the field as "fd" when we really need that kinds of fine-grained synchronization model if it's not enough with SGISTOP, freezer and so. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: Re: [PATCH v2 2/5] mm: introduce external memory hinting API Date: Tue, 21 Jan 2020 10:43:29 -0800 Message-ID: <20200121184329.GG140922@google.com> References: <20200116235953.163318-1-minchan@kernel.org> <20200116235953.163318-3-minchan@kernel.org> <20200117115225.GV19428@dhcp22.suse.cz> <20200120112722.GY18451@dhcp22.suse.cz> <20200120123935.onlls7enjtzenbvt@box> <20200120132405.GF18451@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200120132405.GF18451-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Michal Hocko Cc: "Kirill A. Shutemov" , Kirill Tkhai , Andrew Morton , LKML , linux-mm , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, oleksandr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Johannes Weiner , Shakeel Butt , John Dias , christian.brauner-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org, sjpark-ebkRAfMGSJGzQB+pC5nmwQ@public.gmane.org List-Id: linux-api@vger.kernel.org On Mon, Jan 20, 2020 at 02:24:05PM +0100, Michal Hocko wrote: > On Mon 20-01-20 15:39:35, Kirill A. Shutemov wrote: > > On Mon, Jan 20, 2020 at 12:27:22PM +0100, Michal Hocko wrote: > > > On Mon 20-01-20 13:24:35, Kirill Tkhai wrote: > [...] > > > > Even two threads on common memory need a synchronization > > > > to manage mappings in a sane way. Managing memory from two processes > > > > is the same in principle, and the only difference is that another level > > > > of synchronization is required. > > > > > > Well, not really. The operation might simply attempt to perform an > > > operation on a specific memory area and get a failure if it doesn't > > > reference the same object anymore. What I think we need is some form of > > > a handle to operate on. In the past we have discussed several > > > directions. I was proposing /proc/self/map_anon/ (analogous to > > > map_files) where you could inspect anonymous memory and get a file > > > handle for it. madvise would then operate on the fd and then there > > > shouldn't be a real problem to revalidate that the object is still > > > valid. But there was no general enthusiasm about that approach. There > > > are likely some land mines on the way. > > > > Converting anon memory to file-backed is bad idea and going to backfire. > > I didn't mean to convert. I meant to expose that information via proc > the same way we do for file backed mappings. That shouldn't really > require to re-design the way how anonymous vma work IMO. But I haven't > tried that so there might be many gotchas there. > > There are obvious things to think about though. Such fd cannot be sent > to other processes (SCM stuff), mmap of the file would have to be > disallowed and many others I am not aware of. I am not even pushing this > direction because I am not convinced about how viable it is myself. But > it would sound like a nice extension of the existing mechanism we have > and a file based madvise sounds attractive to me as well because we > already have that. I am not a fan of fd based approach but I already reserved last argument of the API as extendable field so we could use the field as "fd" when we really need that kinds of fine-grained synchronization model if it's not enough with SGISTOP, freezer and so.