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=-2.3 required=3.0 tests=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 D531BC76186 for ; Wed, 24 Jul 2019 20:19:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A96BE206BF for ; Wed, 24 Jul 2019 20:19:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392895AbfGXUTU (ORCPT ); Wed, 24 Jul 2019 16:19:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41280 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726430AbfGXTr5 (ORCPT ); Wed, 24 Jul 2019 15:47:57 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 37F2230C1E37; Wed, 24 Jul 2019 19:47:56 +0000 (UTC) Received: from [10.36.116.35] (ovpn-116-35.ams2.redhat.com [10.36.116.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1801918231; Wed, 24 Jul 2019 19:47:24 +0000 (UTC) Subject: Re: [PATCH v2 0/5] mm / virtio: Provide support for page hinting To: "Michael S. Tsirkin" Cc: Nitesh Narayan Lal , Alexander Duyck , kvm@vger.kernel.org, dave.hansen@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, yang.zhang.wz@gmail.com, pagupta@redhat.com, riel@surriel.com, konrad.wilk@oracle.com, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com References: <20190724165158.6685.87228.stgit@localhost.localdomain> <0c520470-4654-cdf2-cf4d-d7c351d25e8b@redhat.com> <20190724153003-mutt-send-email-mst@kernel.org> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwX4EEwECACgFAljj9eoCGwMFCQlmAYAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEE3eEPcA/4Na5IIP/3T/FIQMxIfNzZshIq687qgG 8UbspuE/YSUDdv7r5szYTK6KPTlqN8NAcSfheywbuYD9A4ZeSBWD3/NAVUdrCaRP2IvFyELj xoMvfJccbq45BxzgEspg/bVahNbyuBpLBVjVWwRtFCUEXkyazksSv8pdTMAs9IucChvFmmq3 jJ2vlaz9lYt/lxN246fIVceckPMiUveimngvXZw21VOAhfQ+/sofXF8JCFv2mFcBDoa7eYob s0FLpmqFaeNRHAlzMWgSsP80qx5nWWEvRLdKWi533N2vC/EyunN3HcBwVrXH4hxRBMco3jvM m8VKLKao9wKj82qSivUnkPIwsAGNPdFoPbgghCQiBjBe6A75Z2xHFrzo7t1jg7nQfIyNC7ez MZBJ59sqA9EDMEJPlLNIeJmqslXPjmMFnE7Mby/+335WJYDulsRybN+W5rLT5aMvhC6x6POK z55fMNKrMASCzBJum2Fwjf/VnuGRYkhKCqqZ8gJ3OvmR50tInDV2jZ1DQgc3i550T5JDpToh dPBxZocIhzg+MBSRDXcJmHOx/7nQm3iQ6iLuwmXsRC6f5FbFefk9EjuTKcLMvBsEx+2DEx0E UnmJ4hVg7u1PQ+2Oy+Lh/opK/BDiqlQ8Pz2jiXv5xkECvr/3Sv59hlOCZMOaiLTTjtOIU7Tq 7ut6OL64oAq+zsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCghCj/CA/lc/LMthqQ773ga uB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseBfDXHA6m4B3mUTWo13nid 0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts6TZ+IrPOwT1hfB4WNC+X 2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiuQmt3yqrmN63V9wzaPhC+ xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKBTccu2AXJXWAE1Xjh6GOC 8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvFFFyAS0Nk1q/7EChPcbRb hJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh2YmnmLRTro6eZ/qYwWkC u8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRkF3TwgucpyPtcpmQtTkWS gDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0LLH63+BrrHasfJzxKXzqg rW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4vq7oFCPsOgwARAQABwsFl BBgBAgAPBQJVy5+RAhsMBQkJZgGAAAoJEE3eEPcA/4NagOsP/jPoIBb/iXVbM+fmSHOjEshl KMwEl/m5iLj3iHnHPVLBUWrXPdS7iQijJA/VLxjnFknhaS60hkUNWexDMxVVP/6lbOrs4bDZ NEWDMktAeqJaFtxackPszlcpRVkAs6Msn9tu8hlvB517pyUgvuD7ZS9gGOMmYwFQDyytpepo YApVV00P0u3AaE0Cj/o71STqGJKZxcVhPaZ+LR+UCBZOyKfEyq+ZN311VpOJZ1IvTExf+S/5 lqnciDtbO3I4Wq0ArLX1gs1q1XlXLaVaA3yVqeC8E7kOchDNinD3hJS4OX0e1gdsx/e6COvy qNg5aL5n0Kl4fcVqM0LdIhsubVs4eiNCa5XMSYpXmVi3HAuFyg9dN+x8thSwI836FoMASwOl C7tHsTjnSGufB+D7F7ZBT61BffNBBIm1KdMxcxqLUVXpBQHHlGkbwI+3Ye+nE6HmZH7IwLwV W+Ajl7oYF+jeKaH4DZFtgLYGLtZ1LDwKPjX7VAsa4Yx7S5+EBAaZGxK510MjIx6SGrZWBrrV TEvdV00F2MnQoeXKzD7O4WFbL55hhyGgfWTHwZ457iN9SgYi1JLPqWkZB0JRXIEtjd4JEQcx +8Umfre0Xt4713VxMygW0PnQt5aSQdMD58jHFxTk092mU+yIHj5LeYgvwSgZN4airXk5yRXl SE+xAvmumFBY Organization: Red Hat GmbH Message-ID: Date: Wed, 24 Jul 2019 21:47:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190724153003-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Wed, 24 Jul 2019 19:47:56 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24.07.19 21:31, Michael S. Tsirkin wrote: > On Wed, Jul 24, 2019 at 08:41:33PM +0200, David Hildenbrand wrote: >> On 24.07.19 20:40, Nitesh Narayan Lal wrote: >>> >>> On 7/24/19 12:54 PM, Alexander Duyck wrote: >>>> This series provides an asynchronous means of hinting to a hypervisor >>>> that a guest page is no longer in use and can have the data associated >>>> with it dropped. To do this I have implemented functionality that allows >>>> for what I am referring to as page hinting >>>> >>>> The functionality for this is fairly simple. When enabled it will allocate >>>> statistics to track the number of hinted pages in a given free area. When >>>> the number of free pages exceeds this value plus a high water value, >>>> currently 32, >>> Shouldn't we configure this to a lower number such as 16? >>>> it will begin performing page hinting which consists of >>>> pulling pages off of free list and placing them into a scatter list. The >>>> scatterlist is then given to the page hinting device and it will perform >>>> the required action to make the pages "hinted", in the case of >>>> virtio-balloon this results in the pages being madvised as MADV_DONTNEED >>>> and as such they are forced out of the guest. After this they are placed >>>> back on the free list, and an additional bit is added if they are not >>>> merged indicating that they are a hinted buddy page instead of a standard >>>> buddy page. The cycle then repeats with additional non-hinted pages being >>>> pulled until the free areas all consist of hinted pages. >>>> >>>> I am leaving a number of things hard-coded such as limiting the lowest >>>> order processed to PAGEBLOCK_ORDER, >>> Have you considered making this option configurable at the compile time? >>>> and have left it up to the guest to >>>> determine what the limit is on how many pages it wants to allocate to >>>> process the hints. >>> It might make sense to set the number of pages to be hinted at a time from the >>> hypervisor. >>>> >>>> My primary testing has just been to verify the memory is being freed after >>>> allocation by running memhog 79g on a 80g guest and watching the total >>>> free memory via /proc/meminfo on the host. With this I have verified most >>>> of the memory is freed after each iteration. As far as performance I have >>>> been mainly focusing on the will-it-scale/page_fault1 test running with >>>> 16 vcpus. With that I have seen at most a 2% difference between the base >>>> kernel without these patches and the patches with virtio-balloon disabled. >>>> With the patches and virtio-balloon enabled with hinting the results >>>> largely depend on the host kernel. On a 3.10 RHEL kernel I saw up to a 2% >>>> drop in performance as I approached 16 threads, >>> I think this is acceptable. >>>> however on the the lastest >>>> linux-next kernel I saw roughly a 4% to 5% improvement in performance for >>>> all tests with 8 or more threads. >>> Do you mean that with your patches the will-it-scale/page_fault1 numbers were >>> better by 4-5% over an unmodified kernel? >>>> I believe the difference seen is due to >>>> the overhead for faulting pages back into the guest and zeroing of memory. >>> It may also make sense to test these patches with netperf to observe how much >>> performance drop it is introducing. >>>> Patch 4 is a bit on the large side at about 600 lines of change, however >>>> I really didn't see a good way to break it up since each piece feeds into >>>> the next. So I couldn't add the statistics by themselves as it didn't >>>> really make sense to add them without something that will either read or >>>> increment/decrement them, or add the Hinted state without something that >>>> would set/unset it. As such I just ended up adding the entire thing as >>>> one patch. It makes it a bit bigger but avoids the issues in the previous >>>> set where I was referencing things before they had been added. >>>> >>>> Changes from the RFC: >>>> https://lore.kernel.org/lkml/20190530215223.13974.22445.stgit@localhost.localdomain/ >>>> Moved aeration requested flag out of aerator and into zone->flags. >>>> Moved bounary out of free_area and into local variables for aeration. >>>> Moved aeration cycle out of interrupt and into workqueue. >>>> Left nr_free as total pages instead of splitting it between raw and aerated. >>>> Combined size and physical address values in virtio ring into one 64b value. >>>> >>>> Changes from v1: >>>> https://lore.kernel.org/lkml/20190619222922.1231.27432.stgit@localhost.localdomain/ >>>> Dropped "waste page treatment" in favor of "page hinting" >>> We may still have to try and find a better name for virtio-balloon side changes. >>> As "FREE_PAGE_HINT" and "PAGE_HINTING" are still confusing. >> >> We should have named that free page reporting, but that train already >> has left. > > I think VIRTIO_BALLOON_F_FREE_PAGE_HINT is different and arguably > actually does provide hints. I guess it depends on the point of view (e.g., getting all free pages feels more like a report). But I could also live with using the term reporting in this context. We could go ahead and name it all "page reporting", would also work for me. -- Thanks, David / dhildenb