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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 A40ACC10F27 for ; Tue, 10 Mar 2020 19:13:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 502CE20727 for ; Tue, 10 Mar 2020 19:13:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Uk3i+0Hg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 502CE20727 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0AAC36B000D; Tue, 10 Mar 2020 15:13:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 05A786B000E; Tue, 10 Mar 2020 15:13:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E3DCF6B0010; Tue, 10 Mar 2020 15:13:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0143.hostedemail.com [216.40.44.143]) by kanga.kvack.org (Postfix) with ESMTP id C80846B000D for ; Tue, 10 Mar 2020 15:13:34 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8A97D4995E2 for ; Tue, 10 Mar 2020 19:13:34 +0000 (UTC) X-FDA: 76580401548.26.grain58_5959181312b1d X-HE-Tag: grain58_5959181312b1d X-Filterd-Recvd-Size: 10641 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Tue, 10 Mar 2020 19:13:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583867613; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=QW5g7lbmMvTsHzYHlNqdZQJfE2pRMb6b/7YHKXkWnFI=; b=Uk3i+0HggwS7vZBgll7jGlQ+OddxbUYE4oyLr3kGmSgPvS4h/LWJoKE6EmIaLmVmrMvLa+ mYFX4LPkFhcyO63LUj6MvbTFxFLRoLD/zxdXCayG2ey5jzdh4Kuo3kkvFHq1eEGv73K6V6 Rl6F3v6Wdy5l/Q+8aZjcRbCsmD/PcRo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-406-P4jqKqzSNMWqPo85VCXTUA-1; Tue, 10 Mar 2020 15:13:27 -0400 X-MC-Unique: P4jqKqzSNMWqPo85VCXTUA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D2E4213F7; Tue, 10 Mar 2020 19:13:25 +0000 (UTC) Received: from [10.36.116.71] (ovpn-116-71.ams2.redhat.com [10.36.116.71]) by smtp.corp.redhat.com (Postfix) with ESMTP id 315BD84779; Tue, 10 Mar 2020 19:13:20 +0000 (UTC) Subject: Re: [PATCH v3] virtio-balloon: Switch back to OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM To: David Rientjes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtualization@lists.linux-foundation.org, Jason Wang , Stephen Rothwell , Tyler Sanderson , "Michael S . Tsirkin" , Wei Wang , Alexander Duyck , Nadav Amit , Michal Hocko , Andrew Morton References: <20200310113854.11515-1-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <890da35b-1ac2-9c2e-b42d-96d24d3e0f4c@redhat.com> Date: Tue, 10 Mar 2020 20:13:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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 10.03.20 20:05, David Rientjes wrote: > On Tue, 10 Mar 2020, David Hildenbrand wrote: > >> Commit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker") >> changed the behavior when deflation happens automatically. Instead of >> deflating when called by the OOM handler, the shrinker is used. >> >> However, the balloon is not simply some other slab cache that should be >> shrunk when under memory pressure. The shrinker does not have a concept of >> priorities yet, so this behavior cannot be configured. Eventually once >> that is in place, we might want to switch back after doing proper >> testing. >> >> There was a report that this results in undesired side effects when >> inflating the balloon to shrink the page cache. [1] >> "When inflating the balloon against page cache (i.e. no free memory >> remains) vmscan.c will both shrink page cache, but also invoke the >> shrinkers -- including the balloon's shrinker. So the balloon >> driver allocates memory which requires reclaim, vmscan gets this >> memory by shrinking the balloon, and then the driver adds the >> memory back to the balloon. Basically a busy no-op." >> >> The name "deflate on OOM" makes it pretty clear when deflation should >> happen - after other approaches to reclaim memory failed, not while >> reclaiming. This allows to minimize the footprint of a guest - memory >> will only be taken out of the balloon when really needed. >> >> Keep using the shrinker for VIRTIO_BALLOON_F_FREE_PAGE_HINT, because >> this has no such side effects. Always register the shrinker with >> VIRTIO_BALLOON_F_FREE_PAGE_HINT now. We are always allowed to reuse free >> pages that are still to be processed by the guest. The hypervisor takes >> care of identifying and resolving possible races between processing a >> hinting request and the guest reusing a page. >> >> In contrast to pre commit 71994620bb25 ("virtio_balloon: replace oom >> notifier with shrinker"), don't add a moodule parameter to configure the >> number of pages to deflate on OOM. Can be re-added if really needed. >> Also, pay attention that leak_balloon() returns the number of 4k pages - >> convert it properly in virtio_balloon_oom_notify(). >> >> Testing done by Tyler for future reference: >> Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 >> GB file full of random bytes that we continually cat to /dev/null. >> This fills the page cache as the file is read. Meanwhile we trigger >> the balloon to inflate, with a target size of 53 GB. This setup causes >> the balloon inflation to pressure the page cache as the page cache is >> also trying to grow. Afterwards we shrink the balloon back to zero (so >> total deflate = total inflate). >> >> Without patch (kernel 4.19.0-5): >> Inflation never reaches the target until we stop the "cat file > >> /dev/null" process. Total inflation time was 542 seconds. The longest >> period that made no net forward progress was 315 seconds (see attached >> graph). >> Result of "grep balloon /proc/vmstat" after the test: >> balloon_inflate 154828377 >> balloon_deflate 154828377 >> >> With patch (kernel 5.6.0-rc4+): >> Total inflation duration was 63 seconds. No deflate-queue activity >> occurs when pressuring the page-cache. >> Result of "grep balloon /proc/vmstat" after the test: >> balloon_inflate 12968539 >> balloon_deflate 12968539 >> >> Conclusion: This patch fixes the issue. In the test it reduced >> inflate/deflate activity by 12x, and reduced inflation time by 8.6x. >> But more importantly, if we hadn't killed the "grep balloon >> /proc/vmstat" process then, without the patch, the inflation process >> would never reach the target. >> >> [1] https://www.spinics.net/lists/linux-virtualization/msg40863.html >> >> Reported-by: Tyler Sanderson >> Tested-by: Tyler Sanderson >> Fixes: 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker") >> Cc: Michael S. Tsirkin >> Cc: Wei Wang >> Cc: Alexander Duyck >> Cc: David Rientjes >> Cc: Nadav Amit >> Cc: Michal Hocko >> Cc: Andrew Morton >> Signed-off-by: David Hildenbrand > > Acked-by: David Rientjes > Thanks! > Should this have: > > Cc: stable@vger.kernel.org # 4.19+ I guess as nothing will actually "crash" it's not worth stable. -- Thanks, David / dhildenb