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Wed, 5 Feb 2020 14:48:18 +0000 (UTC) Received: from localhost (ovpn-12-38.pek2.redhat.com [10.72.12.38]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BC77F87B00; Wed, 5 Feb 2020 14:48:14 +0000 (UTC) Date: Wed, 5 Feb 2020 22:48:11 +0800 From: Baoquan He To: Wei Yang Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, x86@kernel.org, Andrew Morton , Oscar Salvador , Michal Hocko , Pavel Tatashin , Dan Williams Subject: Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() Message-ID: <20200205144811.GF26758@MiWiFi-R3L-srv> References: <20191006085646.5768-1-david@redhat.com> <20191006085646.5768-9-david@redhat.com> <20200205095924.GC24162@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205095924.GC24162@richard> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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: Hi Wei Yang, On 02/05/20 at 05:59pm, Wei Yang wrote: > >diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > >index f294918f7211..8dafa1ba8d9f 100644 > >--- a/mm/memory_hotplug.c > >+++ b/mm/memory_hotplug.c > >@@ -393,6 +393,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, > > if (pfn) { > > zone->zone_start_pfn = pfn; > > zone->spanned_pages = zone_end_pfn - pfn; > >+ } else { > >+ zone->zone_start_pfn = 0; > >+ zone->spanned_pages = 0; > > } > > } else if (zone_end_pfn == end_pfn) { > > /* > >@@ -405,34 +408,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, > > start_pfn); > > if (pfn) > > zone->spanned_pages = pfn - zone_start_pfn + 1; > >+ else { > >+ zone->zone_start_pfn = 0; > >+ zone->spanned_pages = 0; > >+ } > > } > > If it is me, I would like to take out these two similar logic out. I also like this style. > > For example: > > if () { > } else if () { > } else { > goto out; Here the last else is unnecessary, right? > } > > Like this, I believe both David and I will be satisfactory. Even though I still think his 2nd resetting is not needed :-) > /* The zone has no valid section */ > if (!pfn) { > zone->zone_start_pfn = 0; > zone->spanned_pages = 0; > } > > out: > zone_span_writeunlock(zone); > > Well, this is just my personal taste :-) > > >- > >- /* > >- * The section is not biggest or smallest mem_section in the zone, it > >- * only creates a hole in the zone. So in this case, we need not > >- * change the zone. But perhaps, the zone has only hole data. Thus > >- * it check the zone has only hole or not. > >- */ > >- pfn = zone_start_pfn; > >- for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUBSECTION) { > >- if (unlikely(!pfn_to_online_page(pfn))) > >- continue; > >- > >- if (page_zone(pfn_to_page(pfn)) != zone) > >- continue; > >- > >- /* Skip range to be removed */ > >- if (pfn >= start_pfn && pfn < end_pfn) > >- continue; > >- > >- /* If we find valid section, we have nothing to do */ > >- zone_span_writeunlock(zone); > >- return; > >- } > >- > >- /* The zone has no valid section */ > >- zone->zone_start_pfn = 0; > >- zone->spanned_pages = 0; > > zone_span_writeunlock(zone); > > } > > > >-- > >2.21.0 > > -- > Wei Yang > Help you, Help me >