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=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 85913C4338F for ; Mon, 9 Aug 2021 16:23:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6301760F25 for ; Mon, 9 Aug 2021 16:23:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232734AbhHIQXy (ORCPT ); Mon, 9 Aug 2021 12:23:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231409AbhHIQXm (ORCPT ); Mon, 9 Aug 2021 12:23:42 -0400 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D7F1C061798 for ; Mon, 9 Aug 2021 09:23:19 -0700 (PDT) Received: by mail-pj1-x1034.google.com with SMTP id gz13-20020a17090b0ecdb0290178c0e0ce8bso348754pjb.1 for ; Mon, 09 Aug 2021 09:23:19 -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=xqaXLRogo+Ll2PSMriYOcTu+iw4Lps3tpE4wZgAxbH8=; b=uZ973D0b3/eLaCn9gd6LCMNpYQWAEFD51O28ckP2+9oWDok1kYY56k0UVtxL6Q0Oqh /tNeCuBmVfeV/pQXihs1LJeWSO0BkXVDlCcG/qODMwn9fSRE3/27S2yLY8QGNx4lGL4m AZDLoumLJZI4cT2TAweXGBUVtvvNub0hf7vCAKLYkDAzFDMAJMooRbA/b3+1IGi7cFcN AFogcbqLE4CspcD7MEUc7OcKFCoKGbl2fUvsbGMRocSCaIGe/B3mc0gbOdMyqdbQNQuz 7HpJMr/Xcowwal0+rLm8b2OL5OL74xmC0S7XMfkxTHrMBfRW0TYqyWFePNGnTvfhutD8 o3BQ== 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=xqaXLRogo+Ll2PSMriYOcTu+iw4Lps3tpE4wZgAxbH8=; b=CmKD3B0lu9NR1xC1a+9IXaguaV0j/c9txcc4bBDh9BH7HFQamY5uwpVGsdvuXNitIq 0GTK2odTKtMP4cUv9/IgV9RXApWeFI0eseu+mVesueFAuBxWqKU2/kYqjxnvTfpOGvDM RtjVT2KuYrVjEHzwGqMQip5DphZ3UkyoUI9G2tnMUWluPPc2164fPbAsKd0LkIzrSVdl cpYDTEuMIol8R9J3TFd8lMj5RkfkDTCY6q1nW5i6iIdYjGu4cj6DEDIOocmWfofolWVs lGWgIPUPEsfQsxAatGnZ2js7y/g+CdTMkfHs0d1f4EQmQ6jrrJNMIX8XEiZmT11tg4jx bKNw== X-Gm-Message-State: AOAM531AUuJJXGSCpext8tWR1tnbbCvw1BEtgraDc3dsQuT4U1sD45yN e3Zhmc5szz1SIgpqa0T0gJ3NQypknSBpHpHILGnknw== X-Google-Smtp-Source: ABdhPJy/tMuGAmhpC2GpB+8cLHbh0SF+BHGEUAlDotAQKPs9wlE+jobxQxhV8DATrtMkn4YK/LIFcxGYLFTnSb1Kq28= X-Received: by 2002:a63:c0a:: with SMTP id b10mr309863pgl.447.1628526198601; Mon, 09 Aug 2021 09:23:18 -0700 (PDT) MIME-Version: 1.0 References: <20210808160823.3553954-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 9 Aug 2021 09:23:07 -0700 Message-ID: Subject: Re: [PATCH v8 1/2] mm: introduce process_mrelease system call To: Shakeel Butt 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 Mon, Aug 9, 2021 at 8:23 AM Shakeel Butt wrote: > > 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 Thanks folks! I'll make the change Christian suggested and will push the next version carrying Acks along, including the one from David which I forgot to carry in this one.