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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 CF09EC2D0DB for ; Thu, 30 Jan 2020 21:36:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 81C2A2083E for ; Thu, 30 Jan 2020 21:36:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="H0LSjrQU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81C2A2083E 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 31F716B038D; Thu, 30 Jan 2020 16:36:29 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2CFB96B038E; Thu, 30 Jan 2020 16:36:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 211D06B038F; Thu, 30 Jan 2020 16:36:29 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0246.hostedemail.com [216.40.44.246]) by kanga.kvack.org (Postfix) with ESMTP id 09D646B038D for ; Thu, 30 Jan 2020 16:36:29 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B7D66180AD804 for ; Thu, 30 Jan 2020 21:36:28 +0000 (UTC) X-FDA: 76435609656.16.shelf77_1b65616c6de12 X-HE-Tag: shelf77_1b65616c6de12 X-Filterd-Recvd-Size: 7789 Received: from mail-il1-f194.google.com (mail-il1-f194.google.com [209.85.166.194]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Thu, 30 Jan 2020 21:36:28 +0000 (UTC) Received: by mail-il1-f194.google.com with SMTP id f10so4374233ils.8 for ; Thu, 30 Jan 2020 13:36:28 -0800 (PST) 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=kmgy5YTSkXUKRp9/UQMqxu8UXHwptRgFx1MTR1gZUIM=; b=H0LSjrQU/4CzttjbWryHXy45XnpaVRoca6QGkYwwS64Ww91BP+5cIftV5PIATABtiJ 25w1rzjalnFZgC242KYn+YVVHiwLIk4ycXfivd63b8+m+6tBGzj2Y1FDNepPeJEEVKZZ VBnp+gr9Fk0AQr75uC0hGa+fic10OQsJ+raS+5ZeH/RfHJYbbhTIPGshk11F43/Gq1xU SuzolbF0/1FY8rvMaKM4apstLBLStfHWk4MkC9eQRsNku68N1LezXh2ymjhD9YVzqGWj JFmtsUpF9oJciDSpiazzrXacDIgzwWdPe0+VBk3BSF3unEhnh/jFHUs8VfnZwPRzcOGI AByg== 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=kmgy5YTSkXUKRp9/UQMqxu8UXHwptRgFx1MTR1gZUIM=; b=EuQqVvJBIRxrBPzRRyTrvrxx6BFQb/QOO+JAZGz+bMsB6BxUUmnKMrYwSMgw1Omoun Iw/mgmyVfX9+eHMtcSjDhC/bnsOqNJYtm1llcbsWm6EIU1eU2+DZnSzKHEj/yhGuvzvD VLBhoS4vqu4yFiddMvYOHY4E5FPpBsHHI75tf5JH0o+h5Tbt7ysuLWdIH9T3Yu9Gr83u 57+KOc2jhJV/W0GVP/G+48xA4R/+Y2XjXm8BzW7IZDqmDZ5mUKE3pn766E2Xt/AxV0tP Qd53W4ysTT71bLGR/a3NqW4rOJusDQkNUq/RW7G7r6s9ySry+V4dXqDh194b8CgvfhZv Clew== X-Gm-Message-State: APjAAAV6c0j5FSjP2wyynmJQ7TAjw6Ki518g7xXrKot4n+XuPpD3tvbK 13vYo1WzLcNCaHGVgvAnFDFOecfHFOc3+9+/HZFY6x3MstkLDQ== X-Google-Smtp-Source: APXvYqyu1fWItrJTm3ohjsVH59mPGsRMemdS97sOlb4Svz/AGOO15vK5GcJ5xpQ3UXwHFEJIufsZnYjkaDUJ7W2Jqmo= X-Received: by 2002:a92:d642:: with SMTP id x2mr6410444ilp.169.1580420186925; Thu, 30 Jan 2020 13:36:26 -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: Luigi Semenzato Date: Thu, 30 Jan 2020 13:36:15 -0800 Message-ID: Subject: Re: [PATCH 1/2] Documentation: clarify limitations of hibernation To: "Rafael J. Wysocki" Cc: 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 1:29 PM Rafael J. Wysocki wrote: > > 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? That is correct. More precisely, preallocate_image_memory() doesn't get enough pages, and then preallocate_image_highmem() either gets nothing, or in any case too little.