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Wed, 6 Nov 2019 16:49:47 +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 DD1F35C1B5; Wed, 6 Nov 2019 16:49:22 +0000 (UTC) Subject: Re: + mm-introduce-reported-pages.patch added to -mm tree To: Michal Hocko , akpm@linux-foundation.org Cc: aarcange@redhat.com, alexander.h.duyck@linux.intel.com, dan.j.williams@intel.com, dave.hansen@intel.com, david@redhat.com, konrad.wilk@oracle.com, lcapitulino@redhat.com, mgorman@techsingularity.net, mm-commits@vger.kernel.org, mst@redhat.com, osalvador@suse.de, pagupta@redhat.com, pbonzini@redhat.com, riel@surriel.com, vbabka@suse.cz, wei.w.wang@intel.com, willy@infradead.org, yang.zhang.wz@gmail.com, linux-mm@kvack.org References: <20191106000547.juQRi83gi%akpm@linux-foundation.org> <20191106121605.GH8314@dhcp22.suse.cz> 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, 6 Nov 2019 11:49:22 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191106121605.GH8314@dhcp22.suse.cz> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: JSqE8yCzOwWuc_TF50lCbQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 11/6/19 7:16 AM, Michal Hocko wrote: > I didn't have time to read through newer versions of this patch series > but I remember there were concerns about this functionality being pulled > into the page allocator previously both by me and Mel [1][2]. Have those = been=20 > addressed? I do not see an ack from Mel or any other MM people. Is there > really a consensus that we want something like that living in the > allocator? > > There has also been a different approach discussed and from [3] > (referenced by the cover letter) I can only see > > : Then Nitesh's solution had changed to the bitmap approach[7]. However i= t > : has been pointed out that this solution doesn't deal with sparse memory= , > : hotplug, and various other issues. > > which looks more like something to be done than a fundamental > roadblocks. I agree. I think the major issue with my series would be the performance drop which we are observing specifically with (MAX_ORDER - 2) as the minimu= m reporting order. That is something I am trying to investigate and see if I can fix it. With (MAX_ORDER - 1), I was able to get a similar performance which Alexand= er has reported. > > [1] http://lkml.kernel.org/r/20190912163525.GV2739@techsingularity.net > [2] http://lkml.kernel.org/r/20190912091925.GM4023@dhcp22.suse.cz > [3] http://lkml.kernel.org/r/29f43d5796feed0dec8e8bb98b187d9dac03b900.cam= el@linux.intel.com > > On Tue 05-11-19 16:05:47, Andrew Morton wrote: >> From: Alexander Duyck >> Subject: mm: introduce Reported pages >> >> In order to pave the way for free page reporting in virtualized >> environments we will need a way to get pages out of the free lists and >> identify those pages after they have been returned. To accomplish this, >> this patch adds the concept of a Reported Buddy, which is essentially >> meant to just be the Uptodate flag used in conjunction with the Buddy pa= ge >> type. >> >> It adds a set of pointers we shall call "reported_boundary" which >> represent the upper boundary between the unreported and reported pages.= =20 >> The general idea is that in order for a page to cross from one side of t= he >> boundary to the other it will need to verify that it went through the >> reporting process. Ultimately a free list has been fully processed when >> the boundary has been moved from the tail all they way up to occupying t= he >> first entry in the list. Without this we would have to manually walk th= e >> entire page list until we have find a page that hasn't been reported. I= n >> my testing this adds as much as 18% additional overhead which would make >> this unattractive as a solution. >> >> One limitation to this approach is that it is essentially a linear searc= h >> and in the case of the free lists we can have pages added to either the >> head or the tail of the list. In order to place limits on this we only >> allow pages to be added before the reported_boundary instead of adding t= o >> the tail itself. An added advantage to this approach is that we should = be >> reducing the overall memory footprint of the guest as it will be more >> likely to recycle warm pages versus trying to allocate the reported page= s >> that were likely evicted from the guest memory. >> >> Since we will only be reporting one zone at a time we keep the boundary >> limited to being defined for just the zone we are currently reporting >> pages from. Doing this we can keep the number of additional pointers >> needed quite small. To flag that the boundaries are in place we use a >> single bit in the zone to indicate that reporting and the boundaries are >> active. >> >> We store the index of the boundary pointer used to track the reported pa= ge >> in the page->index value. Doing this we can avoid unnecessary computati= on >> to determine the index value again. There should be no issues with this >> as the value is unused when the page is in the buddy allocator, and is >> reset as soon as the page is removed from the free list. >> >> Link: http://lkml.kernel.org/r/20191105220219.15144.69031.stgit@localhos= t.localdomain >> Signed-off-by: Alexander Duyck >> Cc: Andrea Arcangeli >> Cc: Dan Williams >> Cc: Dave Hansen >> Cc: David Hildenbrand >> Cc: >> Cc: Luiz Capitulino >> Cc: Matthew Wilcox >> Cc: Mel Gorman >> Cc: Michael S. Tsirkin >> Cc: Michal Hocko >> Cc: Oscar Salvador >> Cc: Pankaj Gupta >> Cc: Paolo Bonzini >> Cc: Rik van Riel >> Cc: Vlastimil Babka >> Cc: Wei Wang >> Cc: Yang Zhang >> Signed-off-by: Andrew Morton --=20 Thanks Nitesh