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[209.132.183.28]) by mx.google.com with ESMTPS id e6si12175719vsl.282.2019.07.24.12.54.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jul 2019 12:54:13 -0700 (PDT) Received-SPF: pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=nitesh@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 52C83308620B; Wed, 24 Jul 2019 19:54:12 +0000 (UTC) Received: from [10.18.17.163] (dhcp-17-163.bos.redhat.com [10.18.17.163]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 501D560A35; Wed, 24 Jul 2019 19:54:06 +0000 (UTC) Subject: Re: [PATCH v2 0/5] mm / virtio: Provide support for page hinting To: David Hildenbrand , "Michael S. Tsirkin" Cc: 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: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; prefer-encrypt=mutual; keydata= mQINBFl4pQoBEADT/nXR2JOfsCjDgYmE2qonSGjkM1g8S6p9UWD+bf7YEAYYYzZsLtbilFTe z4nL4AV6VJmC7dBIlTi3Mj2eymD/2dkKP6UXlliWkq67feVg1KG+4UIp89lFW7v5Y8Muw3Fm uQbFvxyhN8n3tmhRe+ScWsndSBDxYOZgkbCSIfNPdZrHcnOLfA7xMJZeRCjqUpwhIjxQdFA7 n0s0KZ2cHIsemtBM8b2WXSQG9CjqAJHVkDhrBWKThDRF7k80oiJdEQlTEiVhaEDURXq+2XmG jpCnvRQDb28EJSsQlNEAzwzHMeplddfB0vCg9fRk/kOBMDBtGsTvNT9OYUZD+7jaf0gvBvBB lbKmmMMX7uJB+ejY7bnw6ePNrVPErWyfHzR5WYrIFUtgoR3LigKnw5apzc7UIV9G8uiIcZEn C+QJCK43jgnkPcSmwVPztcrkbC84g1K5v2Dxh9amXKLBA1/i+CAY8JWMTepsFohIFMXNLj+B RJoOcR4HGYXZ6CAJa3Glu3mCmYqHTOKwezJTAvmsCLd3W7WxOGF8BbBjVaPjcZfavOvkin0u DaFvhAmrzN6lL0msY17JCZo046z8oAqkyvEflFbC0S1R/POzehKrzQ1RFRD3/YzzlhmIowkM BpTqNBeHEzQAlIhQuyu1ugmQtfsYYq6FPmWMRfFPes/4JUU/PQARAQABtCVOaXRlc2ggTmFy YXlhbiBMYWwgPG5pbGFsQHJlZGhhdC5jb20+iQI9BBMBCAAnBQJZeKUKAhsjBQkJZgGABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEKOGQNwGMqM56lEP/A2KMs/pu0URcVk/kqVwcBhU SnvB8DP3lDWDnmVrAkFEOnPX7GTbactQ41wF/xwjwmEmTzLrMRZpkqz2y9mV0hWHjqoXbOCS 6RwK3ri5e2ThIPoGxFLt6TrMHgCRwm8YuOSJ97o+uohCTN8pmQ86KMUrDNwMqRkeTRW9wWIQ EdDqW44VwelnyPwcmWHBNNb1Kd8j3xKlHtnS45vc6WuoKxYRBTQOwI/5uFpDZtZ1a5kq9Ak/ MOPDDZpd84rqd+IvgMw5z4a5QlkvOTpScD21G3gjmtTEtyfahltyDK/5i8IaQC3YiXJCrqxE r7/4JMZeOYiKpE9iZMtS90t4wBgbVTqAGH1nE/ifZVAUcCtycD0f3egX9CHe45Ad4fsF3edQ ESa5tZAogiA4Hc/yQpnnf43a3aQ67XPOJXxS0Qptzu4vfF9h7kTKYWSrVesOU3QKYbjEAf95 NewF9FhAlYqYrwIwnuAZ8TdXVDYt7Z3z506//sf6zoRwYIDA8RDqFGRuPMXUsoUnf/KKPrtR ceLcSUP/JCNiYbf1/QtW8S6Ca/4qJFXQHp0knqJPGmwuFHsarSdpvZQ9qpxD3FnuPyo64S2N Dfq8TAeifNp2pAmPY2PAHQ3nOmKgMG8Gn5QiORvMUGzSz8Lo31LW58NdBKbh6bci5+t/HE0H pnyVf5xhNC/FuQINBFl4pQoBEACr+MgxWHUP76oNNYjRiNDhaIVtnPRqxiZ9v4H5FPxJy9UD Bqr54rifr1E+K+yYNPt/Po43vVL2cAyfyI/LVLlhiY4yH6T1n+Di/hSkkviCaf13gczuvgz4 KVYLwojU8+naJUsiCJw01MjO3pg9GQ+47HgsnRjCdNmmHiUQqksMIfd8k3reO9SUNlEmDDNB XuSzkHjE5y/R/6p8uXaVpiKPfHoULjNRWaFc3d2JGmxJpBdpYnajoz61m7XJlgwl/B5Ql/6B dHGaX3VHxOZsfRfugwYF9CkrPbyO5PK7yJ5vaiWre7aQ9bmCtXAomvF1q3/qRwZp77k6i9R3 tWfXjZDOQokw0u6d6DYJ0Vkfcwheg2i/Mf/epQl7Pf846G3PgSnyVK6cRwerBl5a68w7xqVU 4KgAh0DePjtDcbcXsKRT9D63cfyfrNE+ea4i0SVik6+N4nAj1HbzWHTk2KIxTsJXypibOKFX 2VykltxutR1sUfZBYMkfU4PogE7NjVEU7KtuCOSAkYzIWrZNEQrxYkxHLJsWruhSYNRsqVBy KvY6JAsq/i5yhVd5JKKU8wIOgSwC9P6mXYRgwPyfg15GZpnw+Fpey4bCDkT5fMOaCcS+vSU1 UaFmC4Ogzpe2BW2DOaPU5Ik99zUFNn6cRmOOXArrryjFlLT5oSOe4IposgWzdwARAQABiQIl BBgBCAAPBQJZeKUKAhsMBQkJZgGAAAoJEKOGQNwGMqM5ELoP/jj9d9gF1Al4+9bngUlYohYu 0sxyZo9IZ7Yb7cHuJzOMqfgoP4tydP4QCuyd9Q2OHHL5AL4VFNb8SvqAxxYSPuDJTI3JZwI7 d8JTPKwpulMSUaJE8ZH9n8A/+sdC3CAD4QafVBcCcbFe1jifHmQRdDrvHV9Es14QVAOTZhnJ vweENyHEIxkpLsyUUDuVypIo6y/Cws+EBCWt27BJi9GH/EOTB0wb+2ghCs/i3h8a+bi+bS7L FCCm/AxIqxRurh2UySn0P/2+2eZvneJ1/uTgfxnjeSlwQJ1BWzMAdAHQO1/lnbyZgEZEtUZJ x9d9ASekTtJjBMKJXAw7GbB2dAA/QmbA+Q+Xuamzm/1imigz6L6sOt2n/X/SSc33w8RJUyor SvAIoG/zU2Y76pKTgbpQqMDmkmNYFMLcAukpvC4ki3Sf086TdMgkjqtnpTkEElMSFJC8npXv 3QnGGOIfFug/qs8z03DLPBz9VYS26jiiN7QIJVpeeEdN/LKnaz5LO+h5kNAyj44qdF2T2AiF HxnZnxO5JNP5uISQH3FjxxGxJkdJ8jKzZV7aT37sC+Rp0o3KNc+GXTR+GSVq87Xfuhx0LRST NK9ZhT0+qkiN7npFLtNtbzwqaqceq3XhafmCiw8xrtzCnlB/C4SiBr/93Ip4kihXJ0EuHSLn VujM7c/b4pps Organization: Red Hat Inc, Message-ID: Date: Wed, 24 Jul 2019 15:54:05 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Wed, 24 Jul 2019 19:54:12 +0000 (UTC) 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 7/24/19 3:47 PM, David Hildenbrand wrote: > 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. I think that should work. Having two separate names one for the kernel and the other for the virtio interface will cause unnecessary confusion. -- Thanks Nitesh