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05 Feb 2020 15:34:14 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,407,1574150400"; d="scan'208";a="264405373" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 05 Feb 2020 15:34:12 -0800 Date: Thu, 6 Feb 2020 07:34:28 +0800 From: Wei Yang To: Baoquan He Subject: Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() Message-ID: <20200205233428.GD28446@richard> References: <20191006085646.5768-1-david@redhat.com> <20191006085646.5768-9-david@redhat.com> <20200205095924.GC24162@richard> <20200205144811.GF26758@MiWiFi-R3L-srv> <20200205225633.GA28446@richard> <20200205230826.GF8965@MiWiFi-R3L-srv> <20200205232620.GC28446@richard> <20200205233051.GG8965@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205233051.GG8965@MiWiFi-R3L-srv> User-Agent: Mutt/1.9.4 (2018-02-28) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Wei Yang Cc: linux-s390@vger.kernel.org, x86@kernel.org, linux-ia64@vger.kernel.org, Pavel Tatashin , David Hildenbrand , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Wei Yang , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Dan Williams , linux-arm-kernel@lists.infradead.org, Oscar Salvador Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Feb 06, 2020 at 07:30:51AM +0800, Baoquan He wrote: >On 02/06/20 at 07:26am, Wei Yang wrote: >> On Thu, Feb 06, 2020 at 07:08:26AM +0800, Baoquan He wrote: >> >On 02/06/20 at 06:56am, Wei Yang wrote: >> >> On Wed, Feb 05, 2020 at 10:48:11PM +0800, Baoquan He wrote: >> >> >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? >> >> > >> >> >> >> I am afraid not. >> >> >> >> If the range is not the first or last, we would leave pfn not initialized. >> > >> >Ah, you are right. I forgot that one. Then pfn can be assigned the >> >zone_start_pfn as the old code. Then the following logic is the same >> >as the original code, find_smallest_section_pfn()/find_biggest_section_pfn() >> >have done the iteration the old for loop was doing. >> > >> > unsigned long pfn = zone_start_pfn; >> > if () { >> > } else if () { >> > } >> > >> > /* The zone has no valid section */ >> > if (!pfn) { >> > zone->zone_start_pfn = 0; >> > zone->spanned_pages = 0; >> > } >> >> This one look better :-) > >Thanks for your confirmation, I will make one patch like this and post. Sure :-) -- Wei Yang Help you, Help me