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 680C8C433EF for ; Tue, 17 May 2022 22:35:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6E6B96B0072; Tue, 17 May 2022 18:35:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 66D806B0073; Tue, 17 May 2022 18:35:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4F6246B0074; Tue, 17 May 2022 18:35:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 38A426B0072 for ; Tue, 17 May 2022 18:35:48 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 05A5520461 for ; Tue, 17 May 2022 22:35:48 +0000 (UTC) X-FDA: 79476693576.13.B65ABDD Received: from mail-lf1-f50.google.com (mail-lf1-f50.google.com [209.85.167.50]) by imf24.hostedemail.com (Postfix) with ESMTP id 404831800ED for ; Tue, 17 May 2022 22:35:36 +0000 (UTC) Received: by mail-lf1-f50.google.com with SMTP id u23so595908lfc.1 for ; Tue, 17 May 2022 15:35:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=/Zs863mmqYrKBlAAx7wNW/MpHeh107LmNRPCsjY50UQ=; b=HiPiHpzszVGhcsUvLnPitbHgIbRAWZNKJIkkaJBC7Sq5O9dTQ2mYcxL5GyyjU5CWzQ 55XFV5hO/s4QGUvkVxwKkC8h04Q9iedN6uqcM7SM1rKekidkegKFTW9vjShPq6tr7Zmg TaUSdeyiRERFSiOONIJ++NlWcpl/P14WO3RTiV285NZgxj6nEMjtaAJqBE1PARyJTaHo 2qsigoa3nhWcBsxJcf/KXperfTP4tbH/byASugDxtckOUezH8EcdHC8ClLzVA6xteWiJ +QGLUECerWEYqHqGlw+CRnewBJ0DPBjKDqMC4UuDstsaDgE4NY/VnlT/h1qnrpFewobT IMdQ== 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=/Zs863mmqYrKBlAAx7wNW/MpHeh107LmNRPCsjY50UQ=; b=mqDImssnUgnpXVp1W/7ly4DSdew5SCNhoENroIppk2WaKHinG1JGhxXivr7eueZW0a bTQOMdG8qVZGjxKBEsrsyGUYSmeICxL6g1x17/ODPMyx8/ltWIuS/ut0EtXlP7zxydCl 7x5I0hRFktIgv1cci05jLUoeyzyARoiCcWjqmgWdvZ6gvGeeO7nn+SkZnmaoWqsDs50t p5+ZtRmHoFNQKp2Y9QDvi56iKq+tvLWd7idVlbp3iI5gnDD8kkqd1RgLC6BG0VyzHo9o ZMJ8LNrdBb6x5wb6EjSEU5qrIYg+zyj9//pd+s+HUh3nD154MaFEM1xb53N/OSPXcDPL bKeg== X-Gm-Message-State: AOAM533YoalmTU1qAi9n/qEsFBVBzwQ5Yx6Llx19rUmaSsVafKT/R3pr LYgg2hmCz2JfqBtN9mSDaUN+TQCfWVlkfcYsLX733g== X-Google-Smtp-Source: ABdhPJy5XddGl0uDodvwJTiqGzHdUfoxLeoqzvAi+F1bOJOFX2DDmCdlW/2iS/G198Pt78gVwFHO/jZ8Yld1KOdye7c= X-Received: by 2002:a05:6512:a88:b0:473:e080:40e8 with SMTP id m8-20020a0565120a8800b00473e08040e8mr18369869lfu.359.1652826945363; Tue, 17 May 2022 15:35:45 -0700 (PDT) MIME-Version: 1.0 References: <20220504214437.2850685-1-zokeefe@google.com> <20220504214437.2850685-5-zokeefe@google.com> In-Reply-To: From: "Zach O'Keefe" Date: Tue, 17 May 2022 15:35:08 -0700 Message-ID: Subject: Re: [PATCH v5 04/13] mm/khugepaged: make hugepage allocation context-specific To: Yang Shi 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: rspam02 X-Rspamd-Queue-Id: 404831800ED X-Stat-Signature: 3xfmq7rydnf8nnbzwkdkf9t14azu5bo4 X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=HiPiHpzs; spf=pass (imf24.hostedemail.com: domain of zokeefe@google.com designates 209.85.167.50 as permitted sender) smtp.mailfrom=zokeefe@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1652826936-329516 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 Tue, May 17, 2022 at 10:51 AM Yang Shi wrote: > > 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. > Sounds good, Yang. I'll take a crack at it for v6. Thanks for taking the time, Zach > > > > Best, > > Zach