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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL autolearn=unavailable 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 85C0DC4320A for ; Wed, 4 Aug 2021 22:55:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DAC66104F for ; Wed, 4 Aug 2021 22:55:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234975AbhHDWz1 (ORCPT ); Wed, 4 Aug 2021 18:55:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231528AbhHDWzZ (ORCPT ); Wed, 4 Aug 2021 18:55:25 -0400 Received: from mail-yb1-xb29.google.com (mail-yb1-xb29.google.com [IPv6:2607:f8b0:4864:20::b29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89FC5C0613D5 for ; Wed, 4 Aug 2021 15:55:12 -0700 (PDT) Received: by mail-yb1-xb29.google.com with SMTP id a201so6085081ybg.12 for ; Wed, 04 Aug 2021 15:55:12 -0700 (PDT) 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=tVCIYEWsJT9t+6yApOAgsgx/mmNe4rHwOe1CneWcSqA=; b=je/d+I73tXt6x535d/iQd245j0n/rAzC5NzaQ5B7vKBA8MDZqAOvvryDLgWWXSKO1N 3sJrAvjB4jPo4sQoDUQu5DL4RbM4f38nTlNxpFzh1aPf8nHZA3pgOcrpf6aTxdaHJ/km eKuhiXAxYBfkVGEA/iO19lJsuN0IRGjfzjUaZdg6ncAnBaGX4uj3Ygxnh9sAFTASeLnF daGtoy+T41ZJp4qyKZvLwyMsXBuJUfhpIjne99lyiHHgq8EUwVwltQlhKDfJL2lzMVES QpbThhNEbqoHA4Sb6DriC2U2F8jR/VbBaZsl11galxs78n165b2UQnXH7znlNqPLNkVc 4hbA== 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=tVCIYEWsJT9t+6yApOAgsgx/mmNe4rHwOe1CneWcSqA=; b=Ho3Yrtq0hnntUUc0amGiXE3WeL6V2m14H4B8FnTDKp3Z4HlSGFJ4hz2Y4GJzV83H6W Pu2V7aORjq4ic5Jjam4vnctHcaZuTKakPFJwDpiauBnJUUUhg181cVVULlmiNSUpFtFI VJoLvcsi2mnp9IS3qLHZsSxwOHEa3Hf2Pwd68mHVJzsJHFsYNWlrwFTbm+iPnbhnIxEV Rw5L5nXo29YEHCo3Sh6jA0djfCK1wZik0N5bOp6zZmtuq5Jow51h4j1mVQu31Zb8+yvZ cJbdiPsF/1WT07QiVbrpPV7EY7+3IIbuychLwdL+Xt5NMq1mVbOb/JLj2oJAXC1IR2cF UL1Q== X-Gm-Message-State: AOAM5313wQWe0vlA6A/kfMiYELYuY7dhPsnzTEgd9sDEXmX2A8CfZ4cI mHs8p6qV+klHw6E46eKGIHhS8LsT2evuHGaAlQLksw== X-Google-Smtp-Source: ABdhPJw8sr/btOOscCL9FUHmBB6W9co69B++CSACaOYEe1NiJsxUUMbxlnN7j7zXEGL2F3RA+ucThpUrZ/F9tfFaB3I= X-Received: by 2002:a25:14d6:: with SMTP id 205mr2474720ybu.250.1628117711518; Wed, 04 Aug 2021 15:55:11 -0700 (PDT) MIME-Version: 1.0 References: <20210804185004.1304692-1-surenb@google.com> <20210804155024.e4e42e1b7b087937271fa7ce@linux-foundation.org> In-Reply-To: <20210804155024.e4e42e1b7b087937271fa7ce@linux-foundation.org> From: Suren Baghdasaryan Date: Wed, 4 Aug 2021 15:55:00 -0700 Message-ID: Subject: Re: [PATCH v6 1/2] mm: introduce process_mrelease system call To: Andrew Morton Cc: Michal Hocko , Michal Hocko , David Rientjes , Matthew Wilcox , Johannes Weiner , Roman Gushchin , Rik van Riel , Minchan Kim , Christian Brauner , Christoph Hellwig , Oleg Nesterov , David Hildenbrand , Jann Horn , Shakeel Butt , Andy Lutomirski , Christian Brauner , Florian Weimer , Jan Engelhardt , Tim Murray , Linux API , linux-mm , LKML , kernel-team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 4, 2021 at 3:50 PM Andrew Morton wrote: > > On Wed, 4 Aug 2021 11:50:03 -0700 Suren Baghdasaryan wrote: > > > In modern systems it's not unusual to have a system component monitoring > > memory conditions of the system and tasked with keeping system memory > > pressure under control. One way to accomplish that is to kill > > non-essential processes to free up memory for more important ones. > > Examples of this are Facebook's OOM killer daemon called oomd and > > Android's low memory killer daemon called lmkd. > > For such system component it's important to be able to free memory > > quickly and efficiently. Unfortunately the time process takes to free > > up its memory after receiving a SIGKILL might vary based on the state > > of the process (uninterruptible sleep), size and OPP level of the core > > the process is running. A mechanism to free resources of the target > > process in a more predictable way would improve system's ability to > > control its memory pressure. > > Introduce process_mrelease system call that releases memory of a dying > > process from the context of the caller. This way the memory is freed in > > a more controllable way with CPU affinity and priority of the caller. > > The workload of freeing the memory will also be charged to the caller. > > The operation is allowed only on a dying process. > > > > After previous discussions [1, 2, 3] the decision was made [4] to introduce > > a dedicated system call to cover this use case. > > > > The API is as follows, > > > > int process_mrelease(int pidfd, unsigned int flags); > > > > DESCRIPTION > > The process_mrelease() system call is used to free the memory of > > an exiting process. > > > > The pidfd selects the process referred to by the PID file > > descriptor. > > (See pidofd_open(2) for further information) > > I did s/pidofd_open/pidfd_open/ Thanks! > > > > > The flags argument is reserved for future use; currently, this > > argument must be specified as 0. > > > > RETURN VALUE > > On success, process_mrelease() returns 0. On error, -1 is > > returned and errno is set to indicate the error. > > > > ERRORS > > EBADF pidfd is not a valid PID file descriptor. > > > > EAGAIN Failed to release part of the address space. > > > > EINTR The call was interrupted by a signal; see signal(7). > > > > EINVAL flags is not 0. > > > > EINVAL The memory of the task cannot be released because the > > process is not exiting, the address space is shared > > with another live process or there is a core dump in > > progress. > > > > ENOSYS This system call is not supported, for example, without > > MMU support built into Linux. > > > > ESRCH The target process does not exist (i.e., it has terminated > > and been waited on). > > > > ... > > > > mm/oom_kill.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 65 insertions(+) > > The code is nice and simple. > > Can we get a test suite into tools/testing/selftests? Let me take a stab at it. Thanks!