From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752833AbeBIUg5 (ORCPT ); Fri, 9 Feb 2018 15:36:57 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:56626 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750909AbeBIUg4 (ORCPT ); Fri, 9 Feb 2018 15:36:56 -0500 Date: Fri, 9 Feb 2018 12:36:15 -0800 From: Andrew Morton To: Pavel Tatashin Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, m.mizuma@jp.fujitsu.com, mhocko@suse.com, catalin.marinas@arm.com, takahiro.akashi@linaro.org, gi-oh.kim@profitbricks.com, heiko.carstens@de.ibm.com, baiyaowei@cmss.chinamobile.com, richard.weiyang@gmail.com, paul.burton@mips.com, miles.chen@mediatek.com, vbabka@suse.cz, mgorman@suse.de, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v3 1/1] mm: initialize pages on demand during boot Message-Id: <20180209123615.4715623481fa07f7b14fd447@linux-foundation.org> In-Reply-To: <20180209192216.20509-2-pasha.tatashin@oracle.com> References: <20180209192216.20509-1-pasha.tatashin@oracle.com> <20180209192216.20509-2-pasha.tatashin@oracle.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 9 Feb 2018 14:22:16 -0500 Pavel Tatashin wrote: > Deferred page initialization allows the boot cpu to initialize a small > subset of the system's pages early in boot, with other cpus doing the rest > later on. > > It is, however, problematic to know how many pages the kernel needs during > boot. Different modules and kernel parameters may change the requirement, > so the boot cpu either initializes too many pages or runs out of memory. > > To fix that, initialize early pages on demand. This ensures the kernel > does the minimum amount of work to initialize pages during boot and leaves > the rest to be divided in the multithreaded initialization path > (deferred_init_memmap). > > The on-demand code is permanently disabled using static branching once > deferred pages are initialized. After the static branch is changed to > false, the overhead is up-to two branch-always instructions if the zone > watermark check fails or if rmqueue fails. lgtm, I'll toss it in for some testing. A couple of tweaks: From: Andrew Morton Subject: mm-initialize-pages-on-demand-during-boot-fix fix typo in comment, make deferred_pages static Cc: Pavel Tatashin Signed-off-by: Andrew Morton --- mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff -puN include/linux/memblock.h~mm-initialize-pages-on-demand-during-boot-fix include/linux/memblock.h diff -puN mm/memblock.c~mm-initialize-pages-on-demand-during-boot-fix mm/memblock.c diff -puN mm/page_alloc.c~mm-initialize-pages-on-demand-during-boot-fix mm/page_alloc.c --- a/mm/page_alloc.c~mm-initialize-pages-on-demand-during-boot-fix +++ a/mm/page_alloc.c @@ -1568,14 +1568,14 @@ static int __init deferred_init_memmap(v } /* - * This lock grantees that only one thread at a time is allowed to grow zones + * This lock guarantees that only one thread at a time is allowed to grow zones * (decrease number of deferred pages). * Protects first_deferred_pfn field in all zones during early boot before * deferred pages are initialized. Deferred pages are initialized in * page_alloc_init_late() soon after smp_init() is complete. */ static __initdata DEFINE_SPINLOCK(deferred_zone_grow_lock); -DEFINE_STATIC_KEY_TRUE(deferred_pages); +static DEFINE_STATIC_KEY_TRUE(deferred_pages); /* * If this zone has deferred pages, try to grow it by initializing enough _