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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 53718C43381 for ; Fri, 8 Mar 2019 19:10:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1DDB2206DF for ; Fri, 8 Mar 2019 19:10:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbfCHTKl (ORCPT ); Fri, 8 Mar 2019 14:10:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48206 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726294AbfCHTKl (ORCPT ); Fri, 8 Mar 2019 14:10:41 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9E056C04D29A; Fri, 8 Mar 2019 19:10:40 +0000 (UTC) Received: from [10.40.205.251] (unknown [10.40.205.251]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 33CCE1001DD4; Fri, 8 Mar 2019 19:10:23 +0000 (UTC) Subject: Re: [RFC][Patch v9 2/6] KVM: Enables the kernel to isolate guest free pages To: Alexander Duyck , "Michael S. Tsirkin" Cc: David Hildenbrand , kvm list , LKML , linux-mm , Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli References: <20190306155048.12868-1-nitesh@redhat.com> <20190306155048.12868-3-nitesh@redhat.com> <2d9ae889-a9b9-7969-4455-ff36944f388b@redhat.com> <22e4b1cd-38a5-6642-8cbe-d68e4fcbb0b7@redhat.com> <78b604be-2129-a716-a7a6-f5b382c9fb9c@redhat.com> <20190307212845-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: <17d2afa6-556e-ec73-40dc-beac536b3f20@redhat.com> Date: Fri, 8 Mar 2019 14:10:20 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="xD6yFrm8IWkNhOHZM6MlHlwxr5wIiR1nl" X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 08 Mar 2019 19:10:40 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --xD6yFrm8IWkNhOHZM6MlHlwxr5wIiR1nl Content-Type: multipart/mixed; boundary="dufyYFqOkdVSep0QbzK5h22WftvV2Qan2"; protected-headers="v1" From: Nitesh Narayan Lal To: Alexander Duyck , "Michael S. Tsirkin" Cc: David Hildenbrand , kvm list , LKML , linux-mm , Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli Message-ID: <17d2afa6-556e-ec73-40dc-beac536b3f20@redhat.com> Subject: Re: [RFC][Patch v9 2/6] KVM: Enables the kernel to isolate guest free pages References: <20190306155048.12868-1-nitesh@redhat.com> <20190306155048.12868-3-nitesh@redhat.com> <2d9ae889-a9b9-7969-4455-ff36944f388b@redhat.com> <22e4b1cd-38a5-6642-8cbe-d68e4fcbb0b7@redhat.com> <78b604be-2129-a716-a7a6-f5b382c9fb9c@redhat.com> <20190307212845-mutt-send-email-mst@kernel.org> In-Reply-To: --dufyYFqOkdVSep0QbzK5h22WftvV2Qan2 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US On 3/8/19 1:06 PM, Alexander Duyck wrote: > On Thu, Mar 7, 2019 at 6:32 PM Michael S. Tsirkin wrot= e: >> On Thu, Mar 07, 2019 at 02:35:53PM -0800, Alexander Duyck wrote: >>> The only other thing I still want to try and see if I can do is to ad= d >>> a jiffies value to the page private data in the case of the buddy >>> pages. >> Actually there's one extra thing I think we should do, and that is mak= e >> sure we do not leave less than X% off the free memory at a time. >> This way chances of triggering an OOM are lower. > If nothing else we could probably look at doing a watermark of some > sort so we have to have X amount of memory free but not hinted before > we will start providing the hints. It would just be a matter of > tracking how much memory we have hinted on versus the amount of memory > that has been pulled from that pool. This is to avoid false OOM in the guest? > It is another reason why we > probably want a bit in the buddy pages somewhere to indicate if a page > has been hinted or not as we can then use that to determine if we have > to account for it in the statistics. The one benefit which I can see of having an explicit bit is that it will help us to have a single hook away from the hot path within buddy merging code (just like your arch_merge_page) and still avoid duplicate hints while releasing pages. I still have to check PG_idle and PG_young which you mentioned but I don't think we can reuse any existing bits. If we really want to have something like a watermark, then can't we use zone->free_pages before isolating to see how many free pages are there and put a threshold on it? (__isolate_free_page() does a similar thing but it does that on per request basis). > >>> With that we could track the age of the page so it becomes >>> easier to only target pages that are truly going cold rather than >>> trying to grab pages that were added to the freelist recently. >> I like that but I have a vague memory of discussing this with Rik van >> Riel and him saying it's actually better to take away recently used >> ones. Can't see why would that be but maybe I remember wrong. Rik - am= I >> just confused? > It is probably to cut down on the need for disk writes in the case of > swap. If that is the case it ends up being a trade off. > > The sooner we hint the less likely it is that we will need to write a > given page to disk. However the sooner we hint, the more likely it is > we will need to trigger a page fault and pull back in a zero page to > populate the last page we were working on. The sweet spot will be that > period of time that is somewhere in between so we don't trigger > unnecessary page faults and we don't need to perform additional swap > reads/writes. --=20 Regards Nitesh --dufyYFqOkdVSep0QbzK5h22WftvV2Qan2-- --xD6yFrm8IWkNhOHZM6MlHlwxr5wIiR1nl Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkXcoRVGaqvbHPuAGo4ZA3AYyozkFAlyCvhwACgkQo4ZA3AYy ozklHg//U4m8Ze127fvPDuSxHHYFcioTxdYLp2hdRLjhbWE4Oe+dBBHYmh53nkzq wWcMhfbDNBDBf1wYcPLEK+i1Hrf0GXyzAFd0XO0W8tOcv4AQi+q7KtZR9ieMaLyo sqxAlflvm+Vn6o89L+6mLW/l/xh/83J6GJjwETBvogCX/z84wx+AaZ4Iq5aV561P h7OpQJdyywMMRE8PRvh3kYGppGqLZ5kDtCbbC4QVOjXM8Hzu40MqJzrqU2rndPHo qOv4cIIBLxmS4nX288aRKSBr9Y6HDs1KnUv8gjwSA6yW0wd5SnZE4CrR4ERNmXc0 KqNABQdpyZI1lEoao8Cf6yGnrPKUmV7Md7NwldWYOiE7/2Oy8AlDJG6xWywU+nHV mgumckUeZiOd7gr8ZLX1W+GlVafa4Sxj8s87rLgaAeC5uyvAAIHA4XzNa3NkdJnW J3bjvxr9DlWKVJoq4n6NUG918u8FH+kdBLmHChJwwB2SN5crCYuMxeEhESGY0jGi 7UzUgF8e3gEHWcnZ4MZ3xsUyxBcFAyhzh5jHmCYqINe10sdZN4ebRqdONFebRS5v MXhRko7axTD7BW1goaaLEwEp7FY7xhNRg1JNeJUfsuWNCl2YnJiR7aobHF93jXjR 3fDCjQ5FQGdkQzkrLwIls+ycXbZ9kktcaOxEvPoU59l2XLbPSLY= =Rc9w -----END PGP SIGNATURE----- --xD6yFrm8IWkNhOHZM6MlHlwxr5wIiR1nl--