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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E57CEC35247 for ; Tue, 4 Feb 2020 16:56:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9DED72087E for ; Tue, 4 Feb 2020 16:56:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FuemFT18" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9DED72087E 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 3CAC76B0006; Tue, 4 Feb 2020 11:56:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 37B576B0007; Tue, 4 Feb 2020 11:56:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 26A616B0008; Tue, 4 Feb 2020 11:56:33 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0094.hostedemail.com [216.40.44.94]) by kanga.kvack.org (Postfix) with ESMTP id 0FBA76B0006 for ; Tue, 4 Feb 2020 11:56:33 -0500 (EST) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id A6D20180AD802 for ; Tue, 4 Feb 2020 16:56:32 +0000 (UTC) X-FDA: 76453048224.01.feast91_390257c83463d X-HE-Tag: feast91_390257c83463d X-Filterd-Recvd-Size: 8137 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [205.139.110.61]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Tue, 4 Feb 2020 16:56:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580835391; 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=YNydENmRwA+pndqgP995+ZDrs7aMQKkRqBlBvhLQorY=; b=FuemFT18OFIowFXuVnRWdZFUB1hafTK8nkSnYDKJ6QAVwUE9s1Q1T5G8memNa/mU5nXK/y sHf8eG4z5JnC/JDgASPLBi64pJeJkOgiLhfaksFVc3oNYvRjSGRQyoWKvRitZhZH9uHkMu FDSKH+O0VMAx3c29RySJCNl+3YTwFmY= 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-322-YmVy2-7ANsi43VDujar6EA-1; Tue, 04 Feb 2020 11:56:29 -0500 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 EEA35190D342; Tue, 4 Feb 2020 16:56:27 +0000 (UTC) Received: from [10.36.116.24] (ovpn-116-24.ams2.redhat.com [10.36.116.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 526C1867FB; Tue, 4 Feb 2020 16:56:23 +0000 (UTC) Subject: Re: Balloon pressuring page cache To: "Michael S. Tsirkin" Cc: Nadav Amit , Alexander Duyck , Tyler Sanderson , "Wang, Wei W" , "virtualization@lists.linux-foundation.org" , David Rientjes , "linux-mm@kvack.org" , Michal Hocko References: <75d4594f-0864-5172-a0f8-f97affedb366@redhat.com> <286AC319A985734F985F78AFA26841F73E3F8A02@shsmsx102.ccr.corp.intel.com> <20200203080520-mutt-send-email-mst@kernel.org> <5ac131de8e3b7fc1fafd05a61feb5f6889aeb917.camel@linux.intel.com> <539B606A-A0CA-4AA4-B99A-759C874A1EF8@vmware.com> <20200204033657-mutt-send-email-mst@kernel.org> <20200204114336-mutt-send-email-mst@kernel.org> 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: Date: Tue, 4 Feb 2020 17:56:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200204114336-mutt-send-email-mst@kernel.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: YmVy2-7ANsi43VDujar6EA-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit 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: [...] >> >> Issue 2: When called via the shrinker, (but also to fix Issue 1), it could be >> that we do have VIRTIO_BALLOON_F_MUST_TELL_HOST. I assume this means >> (-ENOCLUE) that we have to wait until the hypervisor notifies us via the STOP? Or >> for which event do we have to wait? Because there is no way to *tell host* here >> that we want to reuse a page. The hypervisor will *tell us* when we can reuse pages. >> For the shrinker it is simple: Don't use the shrinker with >> VIRTIO_BALLOON_F_MUST_TELL_HOST :) . But to fix Issue 1, we *would* have to wait >> until we get a STOP signal. That is not really possible because it might >> take an infinite amount of time. >> >> Michael, any clue on which event we have to wait with >> VIRTIO_BALLOON_F_MUST_TELL_HOST? IMHO, I don't think >> VIRTIO_BALLOON_F_MUST_TELL_HOST applies to VIRTIO_BALLOON_F_FREE_PAGE_HINT and >> we'd better document that. It introduces complexity with no clear benefit. > > I meant that we must wait for host to see the hint. Signalled via using > the buffer. But maybe that's too far in the meaning from > VIRTIO_BALLOON_F_MUST_TELL_HOST and we need a separate new flag for Yes, that's what I think. > that. Then current code won't be broken (yay!) but we need to > document another flag that's pretty similar. I mean, do we need a flag at all as long as there is no user? Introducing a flag and documenting it if nobody uses it does not sound like a work I will enjoy :) We can simply document "VIRTIO_BALLOON_F_MUST_TELL_HOST does not apply to FREE_PAGE_HINTING" and "with FREE_PAGE_HINTING, the guest can reuse pages any time, without waiting for a response/ack from the hypervisor". Thoughts? -- Thanks, David / dhildenb From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: Balloon pressuring page cache Date: Tue, 4 Feb 2020 17:56:22 +0100 Message-ID: References: <75d4594f-0864-5172-a0f8-f97affedb366@redhat.com> <286AC319A985734F985F78AFA26841F73E3F8A02@shsmsx102.ccr.corp.intel.com> <20200203080520-mutt-send-email-mst@kernel.org> <5ac131de8e3b7fc1fafd05a61feb5f6889aeb917.camel@linux.intel.com> <539B606A-A0CA-4AA4-B99A-759C874A1EF8@vmware.com> <20200204033657-mutt-send-email-mst@kernel.org> <20200204114336-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200204114336-mutt-send-email-mst@kernel.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" To: "Michael S. Tsirkin" Cc: "virtualization@lists.linux-foundation.org" , Tyler Sanderson , "linux-mm@kvack.org" , Nadav Amit , David Rientjes , Alexander Duyck , Michal Hocko List-Id: virtualization@lists.linuxfoundation.org [...] >> >> Issue 2: When called via the shrinker, (but also to fix Issue 1), it could be >> that we do have VIRTIO_BALLOON_F_MUST_TELL_HOST. I assume this means >> (-ENOCLUE) that we have to wait until the hypervisor notifies us via the STOP? Or >> for which event do we have to wait? Because there is no way to *tell host* here >> that we want to reuse a page. The hypervisor will *tell us* when we can reuse pages. >> For the shrinker it is simple: Don't use the shrinker with >> VIRTIO_BALLOON_F_MUST_TELL_HOST :) . But to fix Issue 1, we *would* have to wait >> until we get a STOP signal. That is not really possible because it might >> take an infinite amount of time. >> >> Michael, any clue on which event we have to wait with >> VIRTIO_BALLOON_F_MUST_TELL_HOST? IMHO, I don't think >> VIRTIO_BALLOON_F_MUST_TELL_HOST applies to VIRTIO_BALLOON_F_FREE_PAGE_HINT and >> we'd better document that. It introduces complexity with no clear benefit. > > I meant that we must wait for host to see the hint. Signalled via using > the buffer. But maybe that's too far in the meaning from > VIRTIO_BALLOON_F_MUST_TELL_HOST and we need a separate new flag for Yes, that's what I think. > that. Then current code won't be broken (yay!) but we need to > document another flag that's pretty similar. I mean, do we need a flag at all as long as there is no user? Introducing a flag and documenting it if nobody uses it does not sound like a work I will enjoy :) We can simply document "VIRTIO_BALLOON_F_MUST_TELL_HOST does not apply to FREE_PAGE_HINTING" and "with FREE_PAGE_HINTING, the guest can reuse pages any time, without waiting for a response/ack from the hypervisor". Thoughts? -- Thanks, David / dhildenb