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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D4F34C43331 for ; Wed, 1 Apr 2020 20:27:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8AB3820747 for ; Wed, 1 Apr 2020 20:27:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=soleen.com header.i=@soleen.com header.b="cx66ohga" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8AB3820747 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=soleen.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3E9D38E0009; Wed, 1 Apr 2020 16:27:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 399FC8E0006; Wed, 1 Apr 2020 16:27:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 289C08E0009; Wed, 1 Apr 2020 16:27:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0113.hostedemail.com [216.40.44.113]) by kanga.kvack.org (Postfix) with ESMTP id 113168E0006 for ; Wed, 1 Apr 2020 16:27:46 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B661A181AEF07 for ; Wed, 1 Apr 2020 20:27:45 +0000 (UTC) X-FDA: 76660422090.27.hand56_7defcd1c28a23 X-HE-Tag: hand56_7defcd1c28a23 X-Filterd-Recvd-Size: 7350 Received: from mail-ed1-f65.google.com (mail-ed1-f65.google.com [209.85.208.65]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Wed, 1 Apr 2020 20:27:45 +0000 (UTC) Received: by mail-ed1-f65.google.com with SMTP id cw6so1453546edb.9 for ; Wed, 01 Apr 2020 13:27:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OC9PgTsBjtl+ylJzd7l+Sywlv6FT4l8sZkj2c0W8znk=; b=cx66ohgaUHaRjaRje4/IRGEh9viPuavu+pjiysUzScydyWXf17BsEL/edlAaWb6gm5 5TPSXQZlaWqNNaGkCW1t4SB7YYkDnUTJdfTAysErd1A0wsdZ/G7bJQ7c6vNRq/ghz/en ZKpsZGdHbwrQXbEKwWfQlkvBY0YkUEudsZRuxkDnQbFsuBL8TyuviKplD7YBowU3Fpbz QKsdw4URzuu50/6+xG36rBq36v2V4Mm4oYOE9F4fwObgfhFGiue9lIlIL0MWI6jcHKXQ lZkN6fQLwifC10Qn8SXS/jaKzzBQ2AYCCBWZ9QtIVPxJXJN3iOEBi5rRSSowSG5hiJqF wbtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=OC9PgTsBjtl+ylJzd7l+Sywlv6FT4l8sZkj2c0W8znk=; b=unqwd9EN1JxZzeXOQg+yCIu+KzuTdjrCvGe+DSRjPcoF2kCx7pjcwExXl9kvc+pKsq 9DdbtJf4qy9Ybm4hLsCjRfeB/ayKaz8+xXRAyIYOi3J6beRGeR0HUjnTyU2bO22maI6o /Ek7IxCmmE5q2CG8LGU1NOAM5JjXZqlkN/nPnSvZ21Ri1V4dxMdgHCA81kwyUaV3BIjq Pia3eD1fugFoMt5UkOa4hspQKX6R+D0BzL7S6u04d3TUmmfubgPCR6ht4d0NAEPgeSZe 75vsOM4lbIqKXrP0jO51POplM2RWDCsLA+9NwElhzAP9Hc4kaaDGAMD51iDN65y0cORE IToA== X-Gm-Message-State: ANhLgQ38HhKkGP36V4g5ddk8ZTxebwrClUSsAcmrKY4l0LuhKqTzJtsw t1zGGZjuSwRE1Aj19PBBSAmkt57ScqhNOWW6etef9w== X-Google-Smtp-Source: ADFU+vuq2n4NZBybGxSChO9XkYchxC522ouicWJM9YoOZLujuNAFo22lGfjl8sfv2MWIh69kl1QrZm8eHaoDtRCKsEE= X-Received: by 2002:aa7:c359:: with SMTP id j25mr22523968edr.85.1585772864144; Wed, 01 Apr 2020 13:27:44 -0700 (PDT) MIME-Version: 1.0 References: <20200401193238.22544-1-pasha.tatashin@soleen.com> <20200401195721.GZ22681@dhcp22.suse.cz> In-Reply-To: <20200401195721.GZ22681@dhcp22.suse.cz> From: Pavel Tatashin Date: Wed, 1 Apr 2020 16:27:33 -0400 Message-ID: Subject: Re: [PATCH] mm: initialize deferred pages with interrupts enabled To: Michal Hocko Cc: LKML , Andrew Morton , linux-mm , Dan Williams , Shile Zhang , Daniel Jordan , Kirill Tkhai , David Hildenbrand , James Morris , Sasha Levin Content-Type: text/plain; charset="UTF-8" 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 Wed, Apr 1, 2020 at 3:57 PM Michal Hocko wrote: > > On Wed 01-04-20 15:32:38, Pavel Tatashin wrote: > > Initializing struct pages is a long task and keeping interrupts disabled > > for the duration of this operation introduces a number of problems. > > > > 1. jiffies are not updated for long period of time, and thus incorrect time > > is reported. See proposed solution and discussion here: > > lkml/20200311123848.118638-1-shile.zhang@linux.alibaba.com > > http://lkml.kernel.org/r/20200311123848.118638-1-shile.zhang@linux.alibaba.com > > > 2. It prevents farther improving deferred page initialization by allowing > > inter-node multi-threading. > > > > We are keeping interrupts disabled to solve a rather theoretical problem > > that was never observed in real world (See 3a2d7fa8a3d5). > > > > Lets keep interrupts enabled. In case we ever encounter a scenario where > > an interrupt thread wants to allocate large amount of memory this early in > > boot we can deal with that by growing zone (see deferred_grow_zone()) by > > the needed amount before starting deferred_init_memmap() threads. > > > > Before: > > [ 1.232459] node 0 initialised, 12058412 pages in 1ms > > > > After: > > [ 1.632580] node 0 initialised, 12051227 pages in 436ms > > > > Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages") > > Signed-off-by: Pavel Tatashin > > I would much rather see pgdat_resize_lock completely out of both the > allocator and deferred init path altogether but this can be done in a > separate patch. This one looks slightly safer for stable backports. This is what I wanted to do, but after studying deferred_grow_zone(), I do not see a simple way to solve this. It is one thing to fail an allocation, and it is another thing to have a corruption because of race. > To be completely honest I would love to see the resize lock go away > completely. That might need a deeper thought but I believe it is > something that has never been done properly. > > Acked-by: Michal Hocko Thank you, Pasha > > Thanks! > > > --- > > mm/page_alloc.c | 21 +++++++-------------- > > 1 file changed, 7 insertions(+), 14 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 3c4eb750a199..4498a13b372d 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1792,6 +1792,13 @@ static int __init deferred_init_memmap(void *data) > > BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat)); > > pgdat->first_deferred_pfn = ULONG_MAX; > > > > + /* > > + * Once we unlock here, the zone cannot be grown anymore, thus if an > > + * interrupt thread must allocate this early in boot, zone must be > > + * pre-grown prior to start of deferred page initialization. > > + */ > > + pgdat_resize_unlock(pgdat, &flags); > > + > > /* Only the highest zone is deferred so find it */ > > for (zid = 0; zid < MAX_NR_ZONES; zid++) { > > zone = pgdat->node_zones + zid; > > @@ -1812,8 +1819,6 @@ static int __init deferred_init_memmap(void *data) > > while (spfn < epfn) > > nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn); > > zone_empty: > > - pgdat_resize_unlock(pgdat, &flags); > > - > > /* Sanity check that the next zone really is unpopulated */ > > WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone)); > > > > @@ -1854,18 +1859,6 @@ deferred_grow_zone(struct zone *zone, unsigned int order) > > return false; > > > > pgdat_resize_lock(pgdat, &flags); > > - > > - /* > > - * If deferred pages have been initialized while we were waiting for > > - * the lock, return true, as the zone was grown. The caller will retry > > - * this zone. We won't return to this function since the caller also > > - * has this static branch. > > - */ > > - if (!static_branch_unlikely(&deferred_pages)) { > > - pgdat_resize_unlock(pgdat, &flags); > > - return true; > > - } > > - > > /* > > * If someone grew this zone while we were waiting for spinlock, return > > * true, as there might be enough pages already. > > -- > > 2.17.1 > > > > -- > Michal Hocko > SUSE Labs