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_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham 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 39D6DC4338F for ; Mon, 9 Aug 2021 15:24:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 106B860F93 for ; Mon, 9 Aug 2021 15:24:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234871AbhHIPYT (ORCPT ); Mon, 9 Aug 2021 11:24:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234815AbhHIPYS (ORCPT ); Mon, 9 Aug 2021 11:24:18 -0400 Received: from mail-lj1-x233.google.com (mail-lj1-x233.google.com [IPv6:2a00:1450:4864:20::233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93B6EC061796 for ; Mon, 9 Aug 2021 08:23:57 -0700 (PDT) Received: by mail-lj1-x233.google.com with SMTP id m18so12912352ljo.1 for ; Mon, 09 Aug 2021 08:23:57 -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=GOzOKLELKEmWDNWHZODHt+66wBkXvfqlLeJRQn5bKh8=; b=EsSKEKNSguHCWHnNaZXAJdSFK+muDoE4BRpOTsq/R4/U7d6viU8oHOY08g+H9XSTcz 0wc/4lAgmUsOV5wd0U48asPK9rfqwhO7bh4C3u2W6A5RScfRPmDmxweMPTWVGDRxDJX1 YaXh2OOpWUoLtaoWDs9ePT6APQF6sDGeTEDPUSsSOpgFX7gcULCNVaOvqPSic0kXuBVb cEmjQSPaMGWtDpB/0pzWdklu953XFATM76RYUZVGJW8K8yJWphRAJ5Xwp/e5E1F/gxnq xnJDdsU1LsRlo/mAb/Qydj/IMZwbvzdIz7qcV7dX9bs6Ro99ElOM7Rg0WPXjlwYcyJhh NzFw== 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=GOzOKLELKEmWDNWHZODHt+66wBkXvfqlLeJRQn5bKh8=; b=HKuV3K5b1uVQYZ9Sh0y/YsLdUX2/E63g7BBnnglOivYtB0vEo4KEw/YvUz/GbHuavi YYlXjVsjrXgq0V9tUJ0+4tbdHpTwXw66tMlZlVbCmlW0Is21gZBe4MHILjXgetqW/PUD bee7YMqDsEMi5WymVdhi2uMEQkUHyvhFDhmcYM4G5atSBNKuuPoa7J69DaXYwASd9dmN Po1Vj5aDgvUIDt4GQPkVelIDPTD49L4FpkRpE6ZoqGVcYyAeUeChIEKWKrhRR0kjgP2J WWCzV6P2qMd64GFeSP8nMPMgqye1SOiodUdMVkni+xV190fFJtlvDJIqigupWZqMthxT XV0A== X-Gm-Message-State: AOAM531upitV4P3iaV1CC9x8rl86eXD5TljzAEORLmNnnoIJKRTLu26y iJf2KfjEPWZEdrw+QS5Z5HgP5FpwmV8imbxoaPDKGg== X-Google-Smtp-Source: ABdhPJz1Oe8RmLDeLve77AVbZ54H0TlwHpN0ZXkWDqLj5dCZXTF/CIiUalaGdYAimMOzE6jYQOhglk8Brgg8pM7Zf3Q= X-Received: by 2002:a2e:9954:: with SMTP id r20mr5466500ljj.81.1628522635579; Mon, 09 Aug 2021 08:23:55 -0700 (PDT) MIME-Version: 1.0 References: <20210808160823.3553954-1-surenb@google.com> In-Reply-To: <20210808160823.3553954-1-surenb@google.com> From: Shakeel Butt Date: Mon, 9 Aug 2021 08:23:44 -0700 Message-ID: Subject: Re: [PATCH v8 1/2] mm: introduce process_mrelease system call To: Suren Baghdasaryan Cc: Andrew Morton , 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 , 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-api@vger.kernel.org On Sun, Aug 8, 2021 at 9:08 AM 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 pidfd_open(2) for further information) > > 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). > > [1] https://lore.kernel.org/lkml/20190411014353.113252-3-surenb@google.com/ > [2] https://lore.kernel.org/linux-api/20201113173448.1863419-1-surenb@google.com/ > [3] https://lore.kernel.org/linux-api/20201124053943.1684874-3-surenb@google.com/ > [4] https://lore.kernel.org/linux-api/20201223075712.GA4719@lst.de/ > > Signed-off-by: Suren Baghdasaryan Reviewed-by: Shakeel Butt