From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id 462578E0001 for ; Tue, 22 Jan 2019 10:07:21 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id o21so9576897edq.4 for ; Tue, 22 Jan 2019 07:07:21 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id x22sor21209221eda.18.2019.01.22.07.07.19 for (Google Transport Security); Tue, 22 Jan 2019 07:07:19 -0800 (PST) Date: Tue, 22 Jan 2019 15:07:17 +0000 From: Wei Yang Subject: Re: [PATCH] mm, page_alloc: cleanup usemap_size() when SPARSEMEM is not set Message-ID: <20190122150717.llf4owk6soejibov@master> Reply-To: Wei Yang References: <20190118234905.27597-1-richard.weiyang@gmail.com> <20190122085524.GE4087@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190122085524.GE4087@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Wei Yang , linux-mm@kvack.org, akpm@linux-foundation.org On Tue, Jan 22, 2019 at 09:55:24AM +0100, Michal Hocko wrote: >On Sat 19-01-19 07:49:05, Wei Yang wrote: >> Two cleanups in this patch: >> >> * since pageblock_nr_pages == (1 << pageblock_order), the roundup() >> and right shift pageblock_order could be replaced with >> DIV_ROUND_UP() > >Why is this change worth it? > To make it directly show usemapsize is number of times of pageblock_nr_pages. >> * use BITS_TO_LONGS() to get number of bytes for bitmap >> >> This patch also fix one typo in comment. >> >> Signed-off-by: Wei Yang >> --- >> mm/page_alloc.c | 9 +++------ >> 1 file changed, 3 insertions(+), 6 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index d295c9bc01a8..d7073cedd087 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6352,7 +6352,7 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat, >> /* >> * Calculate the size of the zone->blockflags rounded to an unsigned long >> * Start by making sure zonesize is a multiple of pageblock_order by rounding >> - * up. Then use 1 NR_PAGEBLOCK_BITS worth of bits per pageblock, finally >> + * up. Then use 1 NR_PAGEBLOCK_BITS width of bits per pageblock, finally > >why do you change this? > Is the original comment not correct? Or I misunderstand the English word? >> * round what is now in bits to nearest long in bits, then return it in >> * bytes. >> */ >> @@ -6361,12 +6361,9 @@ static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned l >> unsigned long usemapsize; >> >> zonesize += zone_start_pfn & (pageblock_nr_pages-1); >> - usemapsize = roundup(zonesize, pageblock_nr_pages); >> - usemapsize = usemapsize >> pageblock_order; >> + usemapsize = DIV_ROUND_UP(zonesize, pageblock_nr_pages); >> usemapsize *= NR_PAGEBLOCK_BITS; >> - usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long)); >> - >> - return usemapsize / 8; >> + return BITS_TO_LONGS(usemapsize) * sizeof(unsigned long); >> } >> >> static void __ref setup_usemap(struct pglist_data *pgdat, >> -- >> 2.15.1 >> > >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me