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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49D31C433F5 for ; Tue, 17 May 2022 17:51:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8267E6B0071; Tue, 17 May 2022 13:51:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7D4B76B0073; Tue, 17 May 2022 13:51:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 69DA16B0074; Tue, 17 May 2022 13:51:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 5AF546B0071 for ; Tue, 17 May 2022 13:51:48 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 32AE3608BC for ; Tue, 17 May 2022 17:51:48 +0000 (UTC) X-FDA: 79475977896.02.9441C38 Received: from mail-pj1-f48.google.com (mail-pj1-f48.google.com [209.85.216.48]) by imf23.hostedemail.com (Postfix) with ESMTP id C7FE91400C8 for ; Tue, 17 May 2022 17:51:30 +0000 (UTC) Received: by mail-pj1-f48.google.com with SMTP id oe17-20020a17090b395100b001df77d29587so3214464pjb.2 for ; Tue, 17 May 2022 10:51:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GEkbuRqWkEtmV3y+oJykWGJ5jIp4U6WFyYrK4rJ5avE=; b=Yuwo7GmPdOS6uvq2CHBcTuyPBCdab/k8nBFxUk9bAZQMuA2EgcQ+zZEfDVV6Kd/53O BJjCDRFpNHpPRr6H248gDvFPP01OS0ye5mr13JiaXDVwXICSEy4U/lhN60qvSWzFZSU9 AytgggBdSlPoT4ckhkm/RRsFrIiCYxd0COtlPLh9H3aKTSfQ32P/tqkDImdKgixgZSB0 AmwgZTTTmmdNiRuvzpduDCVkmgeupBqKPVl36oFGH6btQd7VHvWyEameQFDGTxUPKZ0a 3Dyg7/ZYR+sbNxcRqfo5SFFe6FefX1bzK0hO5Lhmkyk6Foh9MhBlRvGeesHvbKPHTmX5 eglg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GEkbuRqWkEtmV3y+oJykWGJ5jIp4U6WFyYrK4rJ5avE=; b=g57HXQB5DqVM4ll3Qs/3R2hlGWJCftHNLDS+hYdU/IJm44dfUilbGQXGc2ArTtds2q dbsMDR3iheBOldhG08Ll9/b0oxYNK9g3VRLkLwTkZIVTnR9LRxs9vs6R1va0rfU2leaL ZcgIsWm4CpHhIaRG6OmyTKBoAyASSF5oq4T1n5nlfeyX3aPNIi46ANxsW5jrcG6vxTF4 +CGIVGFgJ9u8NQmFAjFQqfoVtguCNIPHKvNYMqPVGOYeho1Ip0wSM2FRBrmDqg0y0+Gn Vj4/+mnn2buZJEANt1J7JVw6xlBYVELAWtkO9fWvX/4F2L+ZNRd+U6VWdq/ttun3oMzS zq6g== X-Gm-Message-State: AOAM53349YHW+s8a7HqPupZrYSLLPNi8yiI3va4ZLSFgd2qN7kzADsIb LVnayAhoUc0I2MwDEY8cuRkela8b1ZPOX6BjIvc= X-Google-Smtp-Source: ABdhPJxvoD16pGiS69HJcExS3kKQrNwseJP69Y3NvWdFU+s+CDeiR9cnv/VxYSGq2gjrUKZ6Ohrq4O2KE465cCxXvoc= X-Received: by 2002:a17:90b:1b52:b0:1dc:54ea:ac00 with SMTP id nv18-20020a17090b1b5200b001dc54eaac00mr37681709pjb.99.1652809906713; Tue, 17 May 2022 10:51:46 -0700 (PDT) MIME-Version: 1.0 References: <20220504214437.2850685-1-zokeefe@google.com> <20220504214437.2850685-5-zokeefe@google.com> In-Reply-To: From: Yang Shi Date: Tue, 17 May 2022 10:18:34 -0700 Message-ID: Subject: Re: [PATCH v5 04/13] mm/khugepaged: make hugepage allocation context-specific To: "Zach O'Keefe" Cc: David Rientjes , Alex Shi , David Hildenbrand , Matthew Wilcox , Michal Hocko , Pasha Tatashin , Peter Xu , SeongJae Park , Song Liu , Vlastimil Babka , Zi Yan , Linux MM , Andrea Arcangeli , Andrew Morton , Arnd Bergmann , Axel Rasmussen , Chris Kennelly , Chris Zankel , Helge Deller , Hugh Dickins , Ivan Kokshaysky , "James E.J. Bottomley" , Jens Axboe , "Kirill A. Shutemov" , Matt Turner , Max Filippov , Miaohe Lin , Minchan Kim , Patrick Xia , Pavel Begunkov , Thomas Bogendoerfer Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C7FE91400C8 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=Yuwo7GmP; spf=pass (imf23.hostedemail.com: domain of shy828301@gmail.com designates 209.85.216.48 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Stat-Signature: 8t9s7a5s8hwmjoqbfrriaj4nnqxa64nu X-HE-Tag: 1652809890-942727 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 Fri, May 13, 2022 at 4:56 PM Zach O'Keefe wrote: > > On Fri, May 13, 2022 at 4:17 PM Yang Shi wrote: > > > > On Fri, May 13, 2022 at 4:05 PM Zach O'Keefe wrote: > > > > > > Thanks for the review, David! > > > > > > On Thu, May 12, 2022 at 1:02 PM David Rientjes wrote: > > > > > > > > On Wed, 4 May 2022, Zach O'Keefe wrote: > > > > > > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > > > > index c94bc43dff3e..6095fcb3f07c 100644 > > > > > --- a/mm/khugepaged.c > > > > > +++ b/mm/khugepaged.c > > > > > @@ -92,6 +92,10 @@ struct collapse_control { > > > > > > > > > > /* Last target selected in khugepaged_find_target_node() */ > > > > > int last_target_node; > > > > > + > > > > > + struct page *hpage; > > > > > + int (*alloc_charge_hpage)(struct mm_struct *mm, > > > > > + struct collapse_control *cc); > > > > > }; > > > > > > > > > > /** > > > > > > > > Embedding this function pointer into collapse_contol seems like it would > > > > need some pretty strong rationale. Not to say that it should be a > > > > non-starter, but I think the changelog needs to clearly indicate why this > > > > is better/cleaner than embedding the needed info for a single allocation > > > > and charge function to use. If the callbacks would truly be so different > > > > that unifying them would be more complex, I think this makes sense. > > > > > > Mostly, this boils down to khugepaged having different a allocation > > > pattern for NUMA/UMA ; the former scans the pages first to determine > > > the right node, the latter preallocates before scanning. khugepaged > > > has the luxury on UMA systems of just holding onto a hugepage > > > indefinitely for the next collapse target. > > > > > > For MADV_COLLAPSE, we never preallocate, and so its pattern doesn't > > > depend on NUMA or UMA configs. Trying to avoid "if (khugepaged) ... > > > else" casing, defining this as a context-defined operation seemed > > > appropriate. > > > > > > Collapsing both alloc and charging together was mostly a code > > > cleanliness decision resulting from not wanting to embed a ->gfp() > > > hook (gfp flags are used both by allocation and memcg charging). > > > Alternatively, a .gfp member could exist - it would just need to be > > > refreshed periodically in the khugepaged codepath. > > > > > > That all said - let me take another crack at seeing if I can make this > > > work without the need for a function pointer here. > > > > I had a patch that removed UMA allocation, please refer to > > https://lore.kernel.org/linux-mm/20210817202146.3218-1-shy828301@gmail.com/#t > > > > It was not made upstream due to some requests for further cleanup, but > > unfortunately I haven't got time to look into it yet. > > > > If this page were merged, would that make your life easier? > > Hey Yang, > > First, sorry for missing that patch in the first place. I actually > have some patches queued up that do a similar cleanup of > khugepaged_prealloc_page() that was mentioned, but decided to not > include them here. > > Second, removing the NUMA/UMA story does make this patch easier, I > think (esp since the sched change was dropped for now). This is > something I wanted while writing this series, but without the larger > context referenced in your patch (most users don't build NUMA=n even > on single node systems, and the pcp hugepage lists optimization) > couldn't justify myself. Thanks, it would be better to add this patch into your series as a prerequisite so that you could make the MADV_COLLAPSE easier. I don't think I will be able to find time to rework the patch and solve all the review comments at any time soon. If you'd like to take it, please do it. > > Best, > Zach