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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 4E5BFC2D0DC for ; Thu, 2 Jan 2020 20:01:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1404A21655 for ; Thu, 2 Jan 2020 20:01:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="UdXvDjVj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1404A21655 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A74A08E0006; Thu, 2 Jan 2020 15:01:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A24B48E0003; Thu, 2 Jan 2020 15:01:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C58B8E0006; Thu, 2 Jan 2020 15:01:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0083.hostedemail.com [216.40.44.83]) by kanga.kvack.org (Postfix) with ESMTP id 733868E0003 for ; Thu, 2 Jan 2020 15:01:12 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 168B08249980 for ; Thu, 2 Jan 2020 20:01:12 +0000 (UTC) X-FDA: 76333763184.19.van84_2786e3d8e1d2e X-HE-Tag: van84_2786e3d8e1d2e X-Filterd-Recvd-Size: 5055 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Jan 2020 20:01:11 +0000 (UTC) Received: by mail-pg1-f202.google.com with SMTP id t12so27512160pgs.13 for ; Thu, 02 Jan 2020 12:01:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=kVgpbfrdFyyzSYGGFbgXSziUKzTWcn4XrnhMtwS4vPA=; b=UdXvDjVjDE18h3ONKld18ZfOZW7pR3vFqqyTPrQKJToK5J6AEggZmqaRXy8sZ2CFA9 Q8hB54QeLPLclYtzAaai1ZfJ1InNNuRcXNSzEq94NIQk4I1eV7Yfb4ksENAjx5uiOAm/ lgxAzsq/u++mCnvzKcIrfqNnLhlKPlw2vR3m+DRLq2Y+aVoGusJZIHDSMKLPlmMjQuop CmhDdAZvqSd11vo2jUTfvheqNUr067u9fXcPd2Hz9FUT1z2He6rGmBy0Cvyrf0+l9DIU Jjv1ROxvJPq5vCPyj8KgwfoUAI/7nuxEo81qcSkj37JlWKgFDPo5p1/RLfSIQQOtfbJ4 x7ug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=kVgpbfrdFyyzSYGGFbgXSziUKzTWcn4XrnhMtwS4vPA=; b=skjZFAtuDp7/1W50wLkJ1KrDpDaxwd1E/hpoNYj5/jSpy4RbUKPdl1Og45McR3l+oM UWSsCroF0NiftnsWqj7qfqbdHKX+J79pQDcH/kbyJMh3neKnqlH8rJoI9SqOfXYO1U5G NiUgi4eaYttNQsyAMFdz4Zyy/1RdK3Iq626oyrYvz90W/7520aPyxS2cVbmN+vmHWJGG NQSxIGDVR1umQO+i5dhniQ2W/DmGVv/iuMGuDQwy/pu8E5VwCAu/iQow/cJkAyvrwT5x ymV9vF8Le2eiBsmXcGcxGlmapCZ0pgXUlOfD3BKVX5pbwUUf/wKoegB6mDgFrQOat0sX yKig== X-Gm-Message-State: APjAAAVu6+pKem/ee45s+S6puY9ToQj/8vn57vaO6fHY3/5Ny9LOP/40 f+niRfO3o7qTW6rcExUB54cl/17M9tTko/A= X-Google-Smtp-Source: APXvYqyqK46UMKubGB6NN9jCbFyC4Y753avcxlOHWCVW9wiWyZZLzBYXk1SWlKSxxIqhOwpNyG78HGuDVgRHnLk= X-Received: by 2002:a63:1f0c:: with SMTP id f12mr94044751pgf.247.1577995270594; Thu, 02 Jan 2020 12:01:10 -0800 (PST) Date: Thu, 2 Jan 2020 12:00:51 -0800 In-Reply-To: <20200102200052.51182-1-semenzato@google.com> Message-Id: <20200102200052.51182-2-semenzato@google.com> Mime-Version: 1.0 References: <20200102200052.51182-1-semenzato@google.com> X-Mailer: git-send-email 2.24.1.735.g03f4e72817-goog Subject: [PATCH v2 1/2] Documentation: clarify limitations of hibernation From: Luigi Semenzato To: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, rafael@kernel.org, gpike@google.com, Luigi Semenzato Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Entering hibernation (suspend-to-disk) will fail if the kernel cannot allocate enough memory to create a snapshot of all pages in use; i.e., if memory in use is over 1/2 of total RAM. This patch makes this limitation clearer in the documentation. Without it, users may assume that hibernation can replace suspend-to-RAM when in fact its functionality is more limited. Signed-off-by: Luigi Semenzato --- Documentation/admin-guide/pm/sleep-states.rst | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/pm/sleep-states.rst b/Documentation/admin-guide/pm/sleep-states.rst index cd3a28cb81f4..a2d5632b7856 100644 --- a/Documentation/admin-guide/pm/sleep-states.rst +++ b/Documentation/admin-guide/pm/sleep-states.rst @@ -112,7 +112,9 @@ Hibernation This state (also referred to as Suspend-to-Disk or STD) offers the greatest energy savings and can be used even in the absence of low-level platform support for system suspend. However, it requires some low-level code for resuming the -system to be present for the underlying CPU architecture. +system to be present for the underlying CPU architecture. Additionally, the +current implementation can enter the hibernation state only when memory +usage is sufficiently low (see "Limitations" below). Hibernation is significantly different from any of the system suspend variants. It takes three system state changes to put it into hibernation and two system @@ -149,6 +151,14 @@ Hibernation is supported if the :c:macro:`CONFIG_HIBERNATION` kernel configuration option is set. However, this option can only be set if support for the given CPU architecture includes the low-level code for system resume. +Limitations of Hibernation +========================== + +When entering hibernation, the kernel tries to allocate a chunk of memory large +enough to contain a copy of all pages in use, to use it for the system +snapshot. If the allocation fails, the system cannot hibernate and the +operation fails with ENOMEM. This will happen, for instance, when the total +amount of anonymous pages (process data) exceeds 1/2 of total RAM. Basic ``sysfs`` Interfaces for System Suspend and Hibernation ============================================================= -- 2.24.1.735.g03f4e72817-goog