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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 B257CFA372C for ; Fri, 8 Nov 2019 07:06:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6389E2087E for ; Fri, 8 Nov 2019 07:06:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NcjXAwTl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6389E2087E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EA75F6B0005; Fri, 8 Nov 2019 02:06:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E32886B0007; Fri, 8 Nov 2019 02:06:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D20616B000A; Fri, 8 Nov 2019 02:06:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0072.hostedemail.com [216.40.44.72]) by kanga.kvack.org (Postfix) with ESMTP id B94686B0005 for ; Fri, 8 Nov 2019 02:06:50 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 60831180ACF8F for ; Fri, 8 Nov 2019 07:06:50 +0000 (UTC) X-FDA: 76132227780.28.spoon33_75dcdc6f34d38 X-HE-Tag: spoon33_75dcdc6f34d38 X-Filterd-Recvd-Size: 9334 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Fri, 8 Nov 2019 07:06:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1573196808; 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; bh=Fa8JprF2HCC8fdNMTfoRi4zjw/9bRCMlEjhWFA73Y0I=; b=NcjXAwTl5BEjBSkKza+l2yXWZWnYjl8Dhq3o87jff5IJ3UOeLUj6XZLUjVkljmd+QnCmb4 Ap7W/DdhQGTFu1NK9OjLCYWG1vC2+VNl2IxNB4NXs8Xh5OGGIuERlyAFqg53fy6OnOWEMx Z8nkFjosShtDdHgj93jWOJErKSPY+uU= 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-49-41Z4XlxCNEqSFX4jq-mM8A-1; Fri, 08 Nov 2019 02:06:45 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 53DBE107ACC3; Fri, 8 Nov 2019 07:06:43 +0000 (UTC) Received: from [10.36.116.108] (ovpn-116-108.ams2.redhat.com [10.36.116.108]) by smtp.corp.redhat.com (Postfix) with ESMTP id 84CDC1A7E2; Fri, 8 Nov 2019 07:06:33 +0000 (UTC) Subject: Re: + mm-introduce-reported-pages.patch added to -mm tree To: Alexander Duyck , Michal Hocko Cc: akpm@linux-foundation.org, aarcange@redhat.com, dan.j.williams@intel.com, dave.hansen@intel.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: <20191106121605.GH8314@dhcp22.suse.cz> <20191106165416.GO8314@dhcp22.suse.cz> <4cf64ff9-b099-d50a-5c08-9a8f3a2f52bf@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <131f72aa-c4e6-572d-f616-624316b62842@redhat.com> Date: Fri, 8 Nov 2019 08:06:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: 41Z4XlxCNEqSFX4jq-mM8A-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8; format=flowed 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: >> "for your own idea" - are you saying Nitesh's approach is my idea? I >> hope not, otherwise I would get credit for Rik's and Nitesh's work by >> simply providing review comments. >=20 > Sorry, I was using "your" in the collective sense. I meant Nitesh, Rik, > MST, yourself, and any other folks are working on the bitmap approach. I guess I was misreading it then :) >=20 >> Of course it is okay to fight for your own idea. >> >>> let me reply to the criticisms of my own patchset before you pile on. I >> >> Me (+ Michal): Are these core buddy changes really wanted and required. >> Can we evaluate the alternatives properly. (Michal even proposed >> something very similar to Nitesh's approach before even looking into it) >=20 > That is part of my frustration. Before I even had a chance to explain the > situation you had already jumped in throwing a "I second that" into the > discussion and insisting on comparisons against Nitesh's patch set which = I > have already provided. The different prototypes Nitesh provided are the only alternatives we=20 have. So, to do the discussion that I want to see for a long time, we=20 should evaluate them? >=20 > Nitesh's most recent patch set caused a kernel panic, and when I fixed > that then it is over 30% worse performance wise than my patch set, and > then when Nitesh restricted the order to MAX_ORDER - 1 and added some > logic to check the buddy before taking the lock then it finally became > comparable. Yes, they are protoypes, RFCs. You did the right thing to report the=20 issues so Nitesh can look into them. >=20 >> You: Please take my patch set, it is better than the alternatives >> because of X, for X in {RFC quality, sparse zones, locking internals, >> current performance differences} >=20 > I should have replied to Michal's original question and simply stated tha= t > Mel had not replied to the patches in the last month and a half. I half > suspect that is the reason for Andrew applying it. It put some pressure o= n > others to provide review feedback, which if nothing else I am grateful > for. >=20 > You had inserted the need to compare it against Nitesh's patch set. Which > based on Nitesh's email is likely going to be a little while since he > cannot give me an ETA. So I want us (you, me, Michal, Mel, Dave, ...) to discuss the direction=20 we want to go. I'd love to do this on a design level, instead of having=20 to wait for any patch set. But I guess this is harder to do? And=20 especially as you keep mentioning the performance difference, I think we=20 should evaluate if this is an unsolvable problem or just an issue in the=20 current prototype? I mean people could have a look at Niteshs older series to see how it=20 fundamentally differs to your approach (external tracking). Nitesh might=20 have fixed some things in the mean time, and is replacing the "fake=20 allocation" by page isolation. But I mean, the general approach should=20 be obvious and sufficient for people to make a decision. >=20 >> And all I am requesting is that we do the evaluation, discuss if there >> are really no alternatives, and sort out fundamental issues with >> external tracking. >> >> Michal asked the very same question again at the beginning of this >> thread: "Is there really a consensus" >=20 > Yes, but he also said he is not nacking the patch. It seemed like he is I never NACKed your series either. > deferring to Mel on this so I will try to work with Mel to address his > concerns since he had some feedback that I can act on. Makes perfect sense to me. >=20 > I'll address the comments Mel provided and be submitting a v14 sometime > soon. >=20 >> Reading the replies, "no". >=20 > I get that you think the bitmap approach is the best approach, but the No, I think that a simple external tracking is preferable over the core=20 buddy modifications we have right now. Kernel panics of fixable=20 performance regressions in an RFC are not fundamental issues to me. > fact is it is still invasive, just to different parts of the mm subsystem= . I'd love to see how it uses the page isolation framework, and only has a=20 single hook to queue pages. I don't like the way pages are pulled out of=20 the buddy in Niteshs approach currently. What you have is cleaner. > I would argue that one of my concerns about the hotplug and sparse > handling is that by skipping those for now is essentially hiding what is > likely to be some invasive code, likely not too different from what I had > to deal with with compaction. At this point he adds more data to the zone > struct than my changes, and I suspect as he progresses that may increase > further. > > I do not think it is fair to hold up review and acceptance of this patch > set for performance comparisons with a patch set with no definite ETA. Michal asked "Is there really a consensus". A consensus that we want=20 something like this, not that we want Nitesh's approach. It's just an=20 alternative worth discussing. And if you are reworking your patch set now with Mel, we might get=20 another alternative that everybody is pleased with. Nobody is against=20 reviewing your series - that's perfect, it's against picking it up and=20 sending it upstream. That's my concern an Michals concern if I am not wrong= . > Ideally we should be able to review and provide feedback on this patch se= t > on its own. Since Nitesh's code is in part based on my virio-balloon code I definitely agree, but this here is *not* a reply to your patch set but=20 to "Re: + mm-introduce-reported-pages.patch added to -mm tree" - picking=20 it up for testing. Michals question is completely valid. And I think the=20 discussion started by Michal and me here is completely valid. > anyway it would make more sense to replace my code eventually if/when he > comes up with a better solution. One thing I can do is make sure that my > code is as non-intrusive as possible so that if/when that time comes > reverting it would not be too difficult. --=20 Thanks, David / dhildenb