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=-5.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 2856DC2D0F2 for ; Tue, 31 Mar 2020 14:05:30 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EAF9520838 for ; Tue, 31 Mar 2020 14:05:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="erBGhYLk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EAF9520838 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:38560 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJHWD-0000nG-2r for qemu-devel@archiver.kernel.org; Tue, 31 Mar 2020 10:05:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47454) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJHVG-0000IR-4E for qemu-devel@nongnu.org; Tue, 31 Mar 2020 10:04:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jJHVE-00060l-NW for qemu-devel@nongnu.org; Tue, 31 Mar 2020 10:04:30 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:29289 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jJHVE-00060Q-JO for qemu-devel@nongnu.org; Tue, 31 Mar 2020 10:04:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585663468; 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=9MLKi3hVsWa92fWPVaRnYiUED++tA8U3XyTe3Icms10=; b=erBGhYLkklvMIh7qit3oEP16ig4z/15v0TWC32ak6/Q1e98eyDovGssnHGx2gYfRvR90kn a2IlHVOsxVuxDo2Te9lcxOOzIBVdBsjro9CsLbH0c2QdA3G2uAw7cBJUd4UuVICx9TiEnW 9PI30slyjNGf0XNS3rt8j5nbjr0V6/o= 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-86-RcHVlwR8N-2_gfVY1LSM_Q-1; Tue, 31 Mar 2020 10:04:24 -0400 X-MC-Unique: RcHVlwR8N-2_gfVY1LSM_Q-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B2EE98010FF; Tue, 31 Mar 2020 14:03:32 +0000 (UTC) Received: from [10.36.114.0] (ovpn-114-0.ams2.redhat.com [10.36.114.0]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0B9FE51331; Tue, 31 Mar 2020 14:03:18 +0000 (UTC) Subject: Re: [RFC for Linux] virtio_balloon: Add VIRTIO_BALLOON_F_THP_ORDER to handle THP spilt issue To: "Michael S. Tsirkin" References: <20200326031817-mutt-send-email-mst@kernel.org> <20200326054554-mutt-send-email-mst@kernel.org> <20200331091718-mutt-send-email-mst@kernel.org> <02a393ce-c4b4-ede9-7671-76fa4c19097a@redhat.com> <20200331093300-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, 31 Mar 2020 16:03:18 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200331093300-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pagupta@redhat.com, Alexander Duyck , qemu-devel@nongnu.org, mojha@codeaurora.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, namit@vmware.com, Hui Zhu , akpm@linux-foundation.org, jasowang@redhat.com, Hui Zhu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 31.03.20 15:37, Michael S. Tsirkin wrote: > On Tue, Mar 31, 2020 at 03:32:05PM +0200, David Hildenbrand wrote: >> On 31.03.20 15:24, Michael S. Tsirkin wrote: >>> On Tue, Mar 31, 2020 at 12:35:24PM +0200, David Hildenbrand wrote: >>>> On 26.03.20 10:49, Michael S. Tsirkin wrote: >>>>> On Thu, Mar 26, 2020 at 08:54:04AM +0100, David Hildenbrand wrote: >>>>>> >>>>>> >>>>>>> Am 26.03.2020 um 08:21 schrieb Michael S. Tsirkin : >>>>>>> >>>>>>> =EF=BB=BFOn Thu, Mar 12, 2020 at 09:51:25AM +0100, David Hildenbr= and wrote: >>>>>>>>> On 12.03.20 09:47, Michael S. Tsirkin wrote: >>>>>>>>> On Thu, Mar 12, 2020 at 09:37:32AM +0100, David Hildenbrand wro= te: >>>>>>>>>> 2. You are essentially stealing THPs in the guest. So the fast= est >>>>>>>>>> mapping (THP in guest and host) is gone. The guest won't be ab= le to make >>>>>>>>>> use of THP where it previously was able to. I can imagine this= implies a >>>>>>>>>> performance degradation for some workloads. This needs a prope= r >>>>>>>>>> performance evaluation. >>>>>>>>> >>>>>>>>> I think the problem is more with the alloc_pages API. >>>>>>>>> That gives you exactly the given order, and if there's >>>>>>>>> a larger chunk available, it will split it up. >>>>>>>>> >>>>>>>>> But for balloon - I suspect lots of other users, >>>>>>>>> we do not want to stress the system but if a large >>>>>>>>> chunk is available anyway, then we could handle >>>>>>>>> that more optimally by getting it all in one go. >>>>>>>>> >>>>>>>>> >>>>>>>>> So if we want to address this, IMHO this calls for a new API. >>>>>>>>> Along the lines of >>>>>>>>> >>>>>>>>> struct page *alloc_page_range(gfp_t gfp, unsigned int min_or= der, >>>>>>>>> unsigned int max_order, unsigned int *order) >>>>>>>>> >>>>>>>>> the idea would then be to return at a number of pages in the gi= ven >>>>>>>>> range. >>>>>>>>> >>>>>>>>> What do you think? Want to try implementing that? >>>>>>>> >>>>>>>> You can just start with the highest order and decrement the orde= r until >>>>>>>> your allocation succeeds using alloc_pages(), which would be eno= ugh for >>>>>>>> a first version. At least I don't see the immediate need for a n= ew >>>>>>>> kernel API. >>>>>>> >>>>>>> OK I remember now. The problem is with reclaim. Unless reclaim i= s >>>>>>> completely disabled, any of these calls can sleep. After it wakes= up, >>>>>>> we would like to get the larger order that has become available >>>>>>> meanwhile. >>>>>>> >>>>>> >>>>>> Yes, but that=E2=80=98s a pure optimization IMHO. >>>>>> So I think we should do a trivial implementation first and then se= e what we gain from a new allocator API. Then we might also be able to ju= stify it using real numbers. >>>>>> >>>>> >>>>> Well how do you propose implement the necessary semantics? >>>>> I think we are both agreed that alloc_page_range is more or >>>>> less what's necessary anyway - so how would you approximate it >>>>> on top of existing APIs? >>>> diff --git a/include/linux/balloon_compaction.h b/include/linux/ball= oon_compaction.h >=20 > ..... >=20 >=20 >>>> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c >>>> index 26de020aae7b..067810b32813 100644 >>>> --- a/mm/balloon_compaction.c >>>> +++ b/mm/balloon_compaction.c >>>> @@ -112,23 +112,35 @@ size_t balloon_page_list_dequeue(struct balloo= n_dev_info *b_dev_info, >>>> EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); >>>> =20 >>>> /* >>>> - * balloon_page_alloc - allocates a new page for insertion into the= balloon >>>> - * page list. >>>> + * balloon_pages_alloc - allocates a new page (of at most the given= order) >>>> + * for insertion into the balloon page list. >>>> * >>>> * Driver must call this function to properly allocate a new balloo= n page. >>>> * Driver must call balloon_page_enqueue before definitively removi= ng the page >>>> * from the guest system. >>>> * >>>> + * Will fall back to smaller orders if allocation fails. The order = of the >>>> + * allocated page is stored in page->private. >>>> + * >>>> * Return: struct page for the allocated page or NULL on allocation= failure. >>>> */ >>>> -struct page *balloon_page_alloc(void) >>>> +struct page *balloon_pages_alloc(int order) >>>> { >>>> - struct page *page =3D alloc_page(balloon_mapping_gfp_mask() | >>>> - __GFP_NOMEMALLOC | __GFP_NORETRY | >>>> - __GFP_NOWARN); >>>> - return page; >>>> + struct page *page; >>>> + >>>> + while (order >=3D 0) { >>>> + page =3D alloc_pages(balloon_mapping_gfp_mask() | >>>> + __GFP_NOMEMALLOC | __GFP_NORETRY | >>>> + __GFP_NOWARN, order); >>>> + if (page) { >>>> + set_page_private(page, order); >>>> + return page; >>>> + } >>>> + order--; >>>> + } >>>> + return NULL; >>>> } >>>> -EXPORT_SYMBOL_GPL(balloon_page_alloc); >>>> +EXPORT_SYMBOL_GPL(balloon_pages_alloc); >>>> =20 >>>> /* >>>> * balloon_page_enqueue - inserts a new page into the balloon page = list. >>> >>> >>> I think this will try to invoke direct reclaim from the first iterati= on >>> to free up the max order. >> >> %__GFP_NORETRY: The VM implementation will try only very lightweight >> memory direct reclaim to get some memory under memory pressure (thus i= t >> can sleep). It will avoid disruptive actions like OOM killer. >> >> Certainly good enough for a first version I would say, no? >=20 > Frankly how well that behaves would depend a lot on the workload. > Can regress just as well. >=20 > For the 1st version I'd prefer something that is the least disruptive, > and that IMHO means we only trigger reclaim at all in the same configur= ation > as now - when we can't satisfy the lowest order allocation. Agreed. >=20 > Anything else would be a huge amount of testing with all kind of > workloads. >=20 So doing a "& ~__GFP_RECLAIM" in case order > 0? (as done in GFP_TRANSHUGE_LIGHT) --=20 Thanks, David / dhildenb