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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,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 89217C4338F for ; Mon, 2 Aug 2021 22:14:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7757D6018A for ; Mon, 2 Aug 2021 22:14:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233032AbhHBWOx (ORCPT ); Mon, 2 Aug 2021 18:14:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231944AbhHBWOq (ORCPT ); Mon, 2 Aug 2021 18:14:46 -0400 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3989C061796 for ; Mon, 2 Aug 2021 15:14:35 -0700 (PDT) Received: by mail-qk1-x74a.google.com with SMTP id p123-20020a378d810000b02903ad5730c883so13988061qkd.22 for ; Mon, 02 Aug 2021 15:14:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=cDcDQEZ+ELX7MhcOwNzOOCGfAe7NRcZ5bpy6u2xYIHI=; b=eAZElcb2hIX+9OSTDxDxtO5eY2wmjEdDv4MqPXygDCO3Oy4E/ZGHfTyDlp1YG3IBIj quLjsPL3ih7cF0Ng916kfFiwEwCPlCnFnXbTM+QEXALovJLz3sM8F0r9FIceOKDSahJY 6qUd5UvTfknowyGSsSdKGcJhg3BMVP2QfGRnRG6IGoSus4GN95TYmNI14ZqEf6txgyof S4Qn41DcwfSew8F/9Rrc4QJf1BnBoGOmo6MewE84VktQH70/VeGoXzEdQmW+4oHXHrNr qEjzV9bAhQBInPPWmWfoomR87P01C8FgQgBg2zqTYppXgDj/HCvpZ88wHpxGgRqrtx1J Z4Rw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=cDcDQEZ+ELX7MhcOwNzOOCGfAe7NRcZ5bpy6u2xYIHI=; b=Pm86mMXUJuksNxwi+ALgec7DfWZzg56T0ri53hIGUJX/JLQJaMsPgfzVoBZO4CA7xL smtfIw7iPb5ytQd+t0yP5z8SNn+vgadjNiaomXHQeLegHXmJy9QwVseClb/ekenrPCHt cI5Mp18H70+B0wBJMGQyohOJHcWm2jhkQearZl73KAePDwXukkK/r4QaHKXj1nZ3hFu6 sa1VtsjPeYYwz8rSB2eXSjdxA9RiKcgsTQNBq+DN9njW0cqMPIkL3QvtH4x+3iAD6b2q JyrtNlekJZ8spnUxAV9fTiE5iQ3g6kbB7Hu3siAk1pQPWjd3MLvknd11Ymep/A1GkGw7 gVVA== X-Gm-Message-State: AOAM5319qbRAcmZy58xrnEhOr1UAtj+6YHN2tLUgvUFk/ZO/Mmf9ExT9 +0B7Rc5qkMabQcZGMcFFPxY56w79b8k= X-Google-Smtp-Source: ABdhPJxVUAfHAWT7elLTQxSRi9zIVge8Lt1ionWnShx1zlnB2Cl/0LdieBS0MUYeJnC/RXusu0FkvwAptoE= X-Received: from surenb1.mtv.corp.google.com ([2620:15c:211:200:f862:f0be:225a:c68d]) (user=surenb job=sendgmr) by 2002:a05:6214:2a45:: with SMTP id jf5mr12445893qvb.25.1627942474989; Mon, 02 Aug 2021 15:14:34 -0700 (PDT) Date: Mon, 2 Aug 2021 15:14:30 -0700 Message-Id: <20210802221431.2251210-1-surenb@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.32.0.554.ge1b32706d8-goog Subject: [PATCH v4 1/2] mm: introduce process_mrelease system call From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: mhocko@kernel.org, mhocko@suse.com, rientjes@google.com, willy@infradead.org, hannes@cmpxchg.org, guro@fb.com, riel@surriel.com, minchan@kernel.org, christian@brauner.io, hch@infradead.org, oleg@redhat.com, david@redhat.com, jannh@google.com, shakeelb@google.com, luto@kernel.org, christian.brauner@ubuntu.com, fweimer@redhat.com, jengelh@inai.de, timmurray@google.com, linux-api@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Previously I proposed a number of alternatives to accomplish this: - https://lore.kernel.org/patchwork/patch/1060407 extending pidfd_send_signal to allow memory reaping using oom_reaper thread; - https://lore.kernel.org/patchwork/patch/1338196 extending pidfd_send_signal to reap memory of the target process synchronously from the context of the caller; - https://lore.kernel.org/patchwork/patch/1344419/ to add MADV_DONTNEED support for process_madvise implementing synchronous memory reaping. The end of the last discussion culminated with suggestion to introduce a dedicated system call (https://lore.kernel.org/patchwork/patch/1344418/#1553875) The reasoning was that the new variant of process_madvise a) does not work on an address range b) is destructive c) doesn't share much code at all with the rest of process_madvise >From the userspace point of view it was awkward and inconvenient to provide memory range for this operation that operates on the entire address space. Using special flags or address values to specify the entire address space was too hacky. 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 a process which was sent a SIGKILL signal. The pidfd selects the process referred to by the PID file descriptor. (See pidofd_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 task does not have a pending SIGKILL or its memory is shared with another process with no pending SIGKILL. ENOSYS This system call is not supported by kernels built with no MMU support (CONFIG_MMU=n). ESRCH The target process does not exist (i.e., it has terminated and been waited on). Signed-off-by: Suren Baghdasaryan --- changes in v4: - Replaced mmap_read_lock() with mmap_read_lock_killable(), per Michal Hocko - Added EINTR error in the manual pages documentation mm/oom_kill.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c729a4c4a1ac..86727794b0a8 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include #include @@ -1141,3 +1142,60 @@ void pagefault_out_of_memory(void) out_of_memory(&oc); mutex_unlock(&oom_lock); } + +SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags) +{ +#ifdef CONFIG_MMU + struct mm_struct *mm = NULL; + struct task_struct *task; + unsigned int f_flags; + struct pid *pid; + long ret = 0; + + if (flags != 0) + return -EINVAL; + + pid = pidfd_get_pid(pidfd, &f_flags); + if (IS_ERR(pid)) + return PTR_ERR(pid); + + task = get_pid_task(pid, PIDTYPE_PID); + if (!task) { + ret = -ESRCH; + goto put_pid; + } + + /* + * If the task is dying and in the process of releasing its memory + * then get its mm. + */ + task_lock(task); + if (task_will_free_mem(task) && (task->flags & PF_KTHREAD) == 0) { + mm = task->mm; + mmget(mm); + } + task_unlock(task); + if (!mm) { + ret = -EINVAL; + goto put_task; + } + + if (mmap_read_lock_killable(mm)) { + ret = -EINTR; + goto put_mm; + } + if (!__oom_reap_task_mm(mm)) + ret = -EAGAIN; + mmap_read_unlock(mm); + +put_mm: + mmput(mm); +put_task: + put_task_struct(task); +put_pid: + put_pid(pid); + return ret; +#else + return -ENOSYS; +#endif /* CONFIG_MMU */ +} -- 2.32.0.554.ge1b32706d8-goog