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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 E0B0EC6379D for ; Wed, 25 Nov 2020 15:20:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 32A9E2067D for ; Wed, 25 Nov 2020 15:20:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 32A9E2067D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 22D146B005C; Wed, 25 Nov 2020 10:20:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1DC4D6B0075; Wed, 25 Nov 2020 10:20:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F29E6B0078; Wed, 25 Nov 2020 10:20:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0095.hostedemail.com [216.40.44.95]) by kanga.kvack.org (Postfix) with ESMTP id ED51E6B005C for ; Wed, 25 Nov 2020 10:20:19 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id AE0651EE6 for ; Wed, 25 Nov 2020 15:20:19 +0000 (UTC) X-FDA: 77523301758.02.spark24_3c0b9d527377 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id 85FDF10097AA0 for ; Wed, 25 Nov 2020 15:20:19 +0000 (UTC) X-HE-Tag: spark24_3c0b9d527377 X-Filterd-Recvd-Size: 4760 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Wed, 25 Nov 2020 15:20:18 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 89670AC22; Wed, 25 Nov 2020 15:20:17 +0000 (UTC) Subject: Re: [PATCH] [RFC] init/main: fix broken buffer_init when DEFERRED_STRUCT_PAGE_INIT set To: Lin Feng , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mgorman@techsingularity.net References: <20201123110500.103523-1-linf@wangsu.com> From: Vlastimil Babka Message-ID: <06a3d903-1f27-16c5-b45b-92ec56a47e96@suse.cz> Date: Wed, 25 Nov 2020 16:20:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201123110500.103523-1-linf@wangsu.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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 11/23/20 12:05 PM, Lin Feng wrote: > In the booting phase if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set, > we have following callchain: > > start_kernel > ... > mm_init > mem_init > memblock_free_all > reset_all_zones_managed_pages > free_low_memory_core_early > ... > buffer_init > nr_free_buffer_pages > zone->managed_pages > ... > rest_init > kernel_init > kernel_init_freeable > page_alloc_init_late > kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid); > wait_for_completion(&pgdat_init_all_done_comp); > ... > files_maxfiles_init > > It's clear that buffer_init depends on zone->managed_pages, but it's reset > in reset_all_zones_managed_pages after that pages are readded into > zone->managed_pages, but when buffer_init runs this process is half done > and most of them will finally be added till deferred_init_memmap done. > In large memory couting of nr_free_buffer_pages drifts too much, also > drifting from kernels to kernels on same hardware. > > Fix is simple, it delays buffer_init run till deferred_init_memmap all done. Hmm nobody should need bh_cachep to allocate buffer heads until then, right. > But as corrected by this patch, max_buffer_heads becomes very large, > the value is roughly as many as 4 times of totalram_pages, formula: > max_buffer_heads = nrpages * (10%) * (PAGE_SIZE / sizeof(struct buffer_head)); > > Say in a 64GB memory box we have 16777216 pages, then max_buffer_heads > turns out to be roughly 67,108,864. > In common cases, should a buffer_head be mapped to one page/block(4KB)? > So max_buffer_heads never exceeds totalram_pages. > IMO it's likely to make buffer_heads_over_limit bool value alwasy false, > then make codes 'if (buffer_heads_over_limit)' test in vmscan unnecessary. > Correct me if it's not true. Maybe we could compile that out with CONFIG_HIGHMEM then? > So this patch will change the original behavior related to > buffer_heads_over_limit in vmscan since we used a half done value > of zone->managed_pages before, or should we use a smaller factor(<10%) in > previous formula. > > Signed-off-by: Lin Feng Acked-by: Vlastimil Babka > --- > init/main.c | 2 -- > mm/page_alloc.c | 3 +++ > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/init/main.c b/init/main.c > index 20baced721ad..a3f7c3416286 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -58,7 +58,6 @@ > #include > #include > #include > -#include > #include > #include > #include > @@ -1034,7 +1033,6 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void) > fork_init(); > proc_caches_init(); > uts_ns_init(); > - buffer_init(); > key_init(); > security_init(); > dbg_late_init(); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index eaa227a479e4..2931d706fb52 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -70,6 +70,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -2103,6 +2104,8 @@ void __init page_alloc_init_late(void) > files_maxfiles_init(); > #endif > > + buffer_init(); > + > /* Discard memblock private memory */ > memblock_discard(); > >