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[2003:cb:c709:6300:a751:d742:1f76:8639]) by smtp.gmail.com with ESMTPSA id l10sm11993306wry.79.2022.02.07.06.50.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Feb 2022 06:50:55 -0800 (PST) Message-ID: Date: Mon, 7 Feb 2022 15:50:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH 2/4] mm/memory_hotplug: avoid calling zone_intersects() for ZONE_NORMAL Content-Language: en-US To: Miaohe Lin , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220207133643.23427-1-linmiaohe@huawei.com> <20220207133643.23427-3-linmiaohe@huawei.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220207133643.23427-3-linmiaohe@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.02.22 14:36, Miaohe Lin wrote: > If zid reaches ZONE_NORMAL, the caller will always get the NORMAL zone no > matter what zone_intersects() returns. So we can save some possible cpu > cycles by avoid calling zone_intersects() for ZONE_NORMAL. > > Signed-off-by: Miaohe Lin > --- > mm/memory_hotplug.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index cbc67c27e0dd..140809e60e9a 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -826,7 +826,7 @@ static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn > struct pglist_data *pgdat = NODE_DATA(nid); > int zid; > > - for (zid = 0; zid <= ZONE_NORMAL; zid++) { > + for (zid = 0; zid < ZONE_NORMAL; zid++) { > struct zone *zone = &pgdat->node_zones[zid]; > > if (zone_intersects(zone, start_pfn, nr_pages)) Makes sense, although we just don't care about the CPU cycles at that point. Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb