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=-13.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 D162EC5519F for ; Wed, 18 Nov 2020 19:22:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7572A2225B for ; Wed, 18 Nov 2020 19:22:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CSfiTZgw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727442AbgKRTWe (ORCPT ); Wed, 18 Nov 2020 14:22:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726635AbgKRTWe (ORCPT ); Wed, 18 Nov 2020 14:22:34 -0500 Received: from mail-wm1-x342.google.com (mail-wm1-x342.google.com [IPv6:2a00:1450:4864:20::342]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A7917C0613D6 for ; Wed, 18 Nov 2020 11:22:33 -0800 (PST) Received: by mail-wm1-x342.google.com with SMTP id d142so4132952wmd.4 for ; Wed, 18 Nov 2020 11:22:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=L5dNLVflsoCWnQaHKvWs9L85VwqNp8UsUbv9wLjV6qI=; b=CSfiTZgwKRZkrhto0srzY8T5NgHeQ5ORWlbLYsBr+wleRBGDbQDMXoZAaO0ImJkt44 jwnxeYw9ySf6N0viXo1ZcV64DhaoZ0waV3olM/pLP9EoWTCMkWpn1fvzhj7igXt+RiKS aRYG8y/aHSDoPLPigh7MEIoTmW4wkXE3u3bjIyAtzAPAEKeO4naRZ2sJSyH7urs+Ujsr pCZNfHkkc4U5LhbQLLyiyqN4BRxyn7xaCOK5xs9LvJ6pGS0EGLTdkaym2GHKptayy67e 9FNlpEBX72O6mZZnO8CLkmo1z52bU6CnYLzM9eHk8pCVaHrzCjx2IPnSPK6v+oK7aM6c xKxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=L5dNLVflsoCWnQaHKvWs9L85VwqNp8UsUbv9wLjV6qI=; b=EGCC5q1kk4R5o2YFCm37EvO3dt3gR2iMIeh85WFzwUoz0vFCWsWmpOTfox5vSYQFLq JxdNH8mhC1XW59wLjseiGlIfTSuSQSBGNJZegMvsJUXd3bPNgd61YaRbv/HwarEwEWky 3RevfOUKhGtgy6SSKaQxUrY7Bz9tIdt4lh2UfF65fPTOfcEQ3WrMIzKCBNUdOuam6J+m DcxkdB8TV/zwWkvBvrd0IWORNCn8YaqojbTa5//u8KsFKzVjJ9hWOpx1oCdb1oqF4IjQ wGp9DbEkZaDEuKAnMhF/3HVyM7f5UkJqGOn8VEQXPSTQc5AnvZ956BbpTxxFRY3+8k54 vJhw== X-Gm-Message-State: AOAM531twTVKRUn48VrccyELVjf2FnReQU8Wmm07PAfJLUJL1EY0bjhB wkG1bNEGhohz4raEpqLHlIsTWNHjJIpWc7k207L4PA== X-Google-Smtp-Source: ABdhPJzHNJdt2+p/Yo25GoJt90AE0ooYZPZ68TX49xvJioavYYVR8ran9z9fFt/Dpl/fTIF6NbpaoSWngZlQbFpfAtY= X-Received: by 2002:a1c:e3c1:: with SMTP id a184mr660962wmh.88.1605727352121; Wed, 18 Nov 2020 11:22:32 -0800 (PST) MIME-Version: 1.0 References: <20201113173448.1863419-1-surenb@google.com> <20201113155539.64e0af5b60ad3145b018ab0d@linux-foundation.org> <20201113170032.7aa56ea273c900f97e6ccbdc@linux-foundation.org> <20201113171810.bebf66608b145cced85bf54c@linux-foundation.org> <20201113181632.6d98489465430a987c96568d@linux-foundation.org> <20201118154334.GT12284@dhcp22.suse.cz> In-Reply-To: <20201118154334.GT12284@dhcp22.suse.cz> From: Suren Baghdasaryan Date: Wed, 18 Nov 2020 11:22:21 -0800 Message-ID: Subject: Re: [PATCH 1/1] RFC: add pidfd_send_signal flag to reclaim mm while killing a process To: Michal Hocko Cc: Andrew Morton , David Rientjes , Matthew Wilcox , Johannes Weiner , Roman Gushchin , Rik van Riel , Christian Brauner , Oleg Nesterov , Tim Murray , linux-api@vger.kernel.org, linux-mm , LKML , kernel-team , Minchan Kim Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 18, 2020 at 11:10 AM Michal Hocko wrote: > > On Fri 13-11-20 18:16:32, Andrew Morton wrote: > [...] > > It's all sounding a bit painful (but not *too* painful). But to > > reiterate, I do think that adding the ability for a process to shoot > > down a large amount of another process's memory is a lot more generally > > useful than tying it to SIGKILL, agree? > > I am not sure TBH. Is there any reasonable usecase where uncoordinated > memory tear down is OK and a target process which is able to see the > unmapped memory? I think uncoordinated memory tear down is a special case which makes sense only when the target process is being killed (and we can enforce that by allowing MADV_DONTNEED to be used only if the target process has pending SIGKILL). However, the ability to apply other flavors of process_madvise() to large memory areas spanning multiple VMAs can be useful in more cases. For example in Android we will use process_madvise(MADV_PAGEOUT) to "shrink" an inactive background process. Today we have to read /proc/maps and construct the vector of VMAs even when applying this advice to the entire process. With such a special mode we could achieve this more efficiently and with less hussle. > -- > Michal Hocko > SUSE Labs