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=-1.0 required=3.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 54B64C3F68F for ; Thu, 30 Jan 2020 21:29:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2102E20674 for ; Thu, 30 Jan 2020 21:29:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2102E20674 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 93FBB6B0389; Thu, 30 Jan 2020 16:29:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8EF986B038A; Thu, 30 Jan 2020 16:29:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 82CBE6B038B; Thu, 30 Jan 2020 16:29:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0136.hostedemail.com [216.40.44.136]) by kanga.kvack.org (Postfix) with ESMTP id 6FBB76B0389 for ; Thu, 30 Jan 2020 16:29:50 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 316C44DBC for ; Thu, 30 Jan 2020 21:29:50 +0000 (UTC) X-FDA: 76435592940.19.bait86_72ea5aa22f53c X-HE-Tag: bait86_72ea5aa22f53c X-Filterd-Recvd-Size: 6669 Received: from mail-oi1-f196.google.com (mail-oi1-f196.google.com [209.85.167.196]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Thu, 30 Jan 2020 21:29:49 +0000 (UTC) Received: by mail-oi1-f196.google.com with SMTP id a22so5094485oid.13 for ; Thu, 30 Jan 2020 13:29:49 -0800 (PST) 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=soBhgt6ejO4/2ekR+e8tGWX3kM/LmDzHreUHc+EeF3w=; b=MxhorHlCnN0y7fa9Lf4Tbc2kMeDNs8r3C71dxoHZm0K4qaAmKFm7WDjzI6MIUUAbFL MLesmvnBIKDX7tIdpOsdVtgLi+cMId5jtRLyYQyCuJaMKQ/TiSPzKP7P4EEwpHEjWzz5 JFyAyGlcOqbDCUp67POmZRSuuDQILCkU1EMyy7e+JJ+AP7LK2wqifFlT/7asbFGJhFK+ bguWHIu/AbBDDbgc9NIPDHzq+6TbnHFx3dC/wFy8L9nNb7C3KyAiQsKUL8w64LdWr3dR hb9ypgmfcWNiXlffKtMlb3XP13b30W595WcOCdoLZxY2c8JirtXEusZ6w7nYviSILNYn wJ9Q== X-Gm-Message-State: APjAAAWwujINwAXAG/5NlcWBgppXyNzfa8KwAwgfrVXzIHGrWhYy/krj qh+JfdpjpJq3m3KeoYUP2lC1Tf1Zzr/qfKGrQQQ= X-Google-Smtp-Source: APXvYqzmrxwT5kg4qHFYISAvEGZKVv/ulcjCjrlzB51QlPN+V0/LTyu6B2NTj5sCi1ymxut6dzXFAgD5rAs4g4Pnv0o= X-Received: by 2002:a54:4e96:: with SMTP id c22mr4402249oiy.110.1580419788640; Thu, 30 Jan 2020 13:29:48 -0800 (PST) MIME-Version: 1.0 References: <20191226220205.128664-1-semenzato@google.com> <20191226220205.128664-2-semenzato@google.com> <20200106125352.GB9198@dhcp22.suse.cz> <20200108114952.GR32178@dhcp22.suse.cz> <20200127141637.GL1183@dhcp22.suse.cz> In-Reply-To: From: "Rafael J. Wysocki" Date: Thu, 30 Jan 2020 22:29:37 +0100 Message-ID: Subject: Re: [PATCH 1/2] Documentation: clarify limitations of hibernation To: Luigi Semenzato Cc: "Rafael J. Wysocki" , Michal Hocko , Linux Memory Management List , linux-kernel , Andrew Morton , Geoff Pike 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: On Thu, Jan 30, 2020 at 10:11 PM Luigi Semenzato wrote: > > On Thu, Jan 30, 2020 at 12:50 PM Rafael J. Wysocki wrote: > > > > On Mon, Jan 27, 2020 at 6:21 PM Luigi Semenzato wrote: > > > > > > On Mon, Jan 27, 2020 at 8:28 AM Rafael J. Wysocki wrote: > > > > > > > > On Mon, Jan 27, 2020 at 5:13 PM Luigi Semenzato wrote: > > > > > > > > > > On Mon, Jan 27, 2020 at 6:16 AM Michal Hocko wrote: > > > > > > > > > > > > On Fri 24-01-20 08:37:12, Luigi Semenzato wrote: > > > > > > [...] > > > > > > > The purpose of my documentation patch was to make it clearer that > > > > > > > hibernation may fail in situations in which suspend-to-RAM works; for > > > > > > > instance, when there is no swap, and anonymous pages are over 50% of > > > > > > > total RAM. I will send a new version of the patch which hopefully > > > > > > > makes this clearer. > > > > > > > > > > > > I was under impression that s2disk is pretty much impossible without any > > > > > > swap. > > > > > > > > > > I am not sure what you mean by "swap" here. S2disk needs a swap > > > > > partition for storing the image, but that partition is not used for > > > > > regular swap. > > > > > > > > That's not correct. > > > > > > > > The swap partition (or file) used by s2disk needs to be made active > > > > before it can use it and the mm subsystem is also able to use it for > > > > regular swap then. > > > > > > OK---I had this wrong, thanks. > > > > > > > > If there is no swap, but more than 50% of RAM is free > > > > > or reclaimable, s2disk works fine. If anonymous is more than 50%, > > > > > hibernation can still work, but swap needs to be set up (in addition > > > > > to the space for the hibernation image). The setup is not obvious and > > > > > I don't think that the documentation is clear on this. > > > > > > > > Well, the entire contents of RAM must be preserved, this way or > > > > another, during hibernation. That should be totally obvious to anyone > > > > using it really. > > > > > > Yes, that's obvious. > > > > > > > Some of the RAM contents is copies of data already there in the > > > > filesystems on persistent storage and that does not need to be saved > > > > again. Everything else must be saved and s2disk (and Linux > > > > hibernation in general) uses active swap space to save these things. > > > > This implies that in order to hibernate the system, you generally need > > > > the amount of swap space equal to the size of RAM minus the size of > > > > files mapped into memory. > > > > > > > > So, to be on the safe side, the total amount of swap space to be used > > > > for hibernation needs to match the size of RAM (even though > > > > realistically it may be smaller than that in the majority of cases). > > > > > > This all makes sense, but we do this: > > > > > > -- add resume=/dev/sdc to the command line > > > -- attach a disk (/dev/sdc) with size equal to RAM > > > -- mkswap /dev/sdc > > > -- swapon /dev/sdc > > > -- echo disk > /sys/power/state > > > > > > and the last operation fails with ENOMEM. Are we doing something > > > wrong? Are we hitting some other mm bug? > > > > I would expect this to work, so the fact that it doesn't work for you > > indicates a bug somewhere or at least an assumption that doesn't hold. > > > > Can you please remind me what you do to trigger the unexpected behavior? > > Yes, I create processes that use a large amount of anon memory, more > than 50% of RAM, like this: > > dd if=/dev/zero bs=1G count=1 | sleep infinity > > I think dd has a 2 GB limit, or around that number, so you'll need a > few of those. And then you get -ENOMEM from hibernate_preallocate_memory(), or from somewhere else?