From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id E5B1A8E0001 for ; Thu, 20 Dec 2018 18:50:30 -0500 (EST) Received: by mail-pf1-f198.google.com with SMTP id q64so3125342pfa.18 for ; Thu, 20 Dec 2018 15:50:30 -0800 (PST) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTPS id l7si1662961pfg.245.2018.12.20.15.50.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Dec 2018 15:50:29 -0800 (PST) Message-ID: Subject: Re: [PATCH] mm: check nr_initialised with PAGES_PER_SECTION directly in defer_init() From: Alexander Duyck Date: Thu, 20 Dec 2018 15:50:29 -0800 In-Reply-To: <20181122094807.6985-1-richard.weiyang@gmail.com> References: <20181122094807.6985-1-richard.weiyang@gmail.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Wei Yang , osalvador@suse.de Cc: akpm@linux-foundation.org, linux-mm@kvack.org On Thu, 2018-11-22 at 17:48 +0800, Wei Yang wrote: > When DEFERRED_STRUCT_PAGE_INIT is configured, only the first section of > each node's highest zone is initialized before defer stage. > > static_init_pgcnt is used to store the number of pages like this: > > pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION, > pgdat->node_spanned_pages); > > because we don't want to overflow zone's range. > > But this is not necessary, since defer_init() is called like this: > > memmap_init_zone() > for pfn in [start_pfn, end_pfn) > defer_init(pfn, end_pfn) > > In case (pgdat->node_spanned_pages < PAGES_PER_SECTION), the loop would > stop before calling defer_init(). > > BTW, comparing PAGES_PER_SECTION with node_spanned_pages is not correct, > since nr_initialised is zone based instead of node based. Even > node_spanned_pages is bigger than PAGES_PER_SECTION, its highest zone > would have pages less than PAGES_PER_SECTION. > > Signed-off-by: Wei Yang This all seems to make sense to me, and appears to be a valid improvement. Reviewed-by: Alexander Duyck > --- > include/linux/mmzone.h | 2 -- > mm/page_alloc.c | 13 ++++++------- > 2 files changed, 6 insertions(+), 9 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index ae7a830a21eb..68d7b558924b 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -692,8 +692,6 @@ typedef struct pglist_data { > * is the first PFN that needs to be initialised. > */ > unsigned long first_deferred_pfn; > - /* Number of non-deferred pages */ > - unsigned long static_init_pgcnt; > #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */ > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 76e12179cd5e..b542d82400cf 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -326,8 +326,13 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn) > /* Always populate low zones for address-constrained allocations */ > if (end_pfn < pgdat_end_pfn(NODE_DATA(nid))) > return false; > + > + /* > + * We start only with one section of pages, more pages are added as > + * needed until the rest of deferred pages are initialized. > + */ > nr_initialised++; > - if ((nr_initialised > NODE_DATA(nid)->static_init_pgcnt) && > + if ((nr_initialised > PAGES_PER_SECTION) && > (pfn & (PAGES_PER_SECTION - 1)) == 0) { > NODE_DATA(nid)->first_deferred_pfn = pfn; > return true; > @@ -6451,12 +6456,6 @@ static void __ref alloc_node_mem_map(struct pglist_data *pgdat) { } > #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT > static inline void pgdat_set_deferred_range(pg_data_t *pgdat) > { > - /* > - * We start only with one section of pages, more pages are added as > - * needed until the rest of deferred pages are initialized. > - */ > - pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION, > - pgdat->node_spanned_pages); > pgdat->first_deferred_pfn = ULONG_MAX; > } > #else