From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id F21496B0069 for ; Mon, 2 Jan 2017 10:07:07 -0500 (EST) Received: by mail-wm0-f70.google.com with SMTP id w13so76229908wmw.0 for ; Mon, 02 Jan 2017 07:07:07 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id k188si69800751wmd.64.2017.01.02.07.07.06 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 02 Jan 2017 07:07:06 -0800 (PST) Subject: Re: [PATCH 1/2] mm: fix remote numa hits statistics References: <20161221075711.GF16502@dhcp22.suse.cz> <20161221080653.29437-1-mhocko@kernel.org> <1d9e466b-dc87-eb41-113f-e7737a4bb7ef@suse.cz> <20170102144634.GB18048@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: Date: Mon, 2 Jan 2017 16:07:05 +0100 MIME-Version: 1.0 In-Reply-To: <20170102144634.GB18048@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, Mel Gorman , Andrew Morton , Joonsoo Kim , Jia He , Taku Izumi , Johannes Weiner On 01/02/2017 03:46 PM, Michal Hocko wrote: > On Mon 02-01-17 15:16:23, Vlastimil Babka wrote: >> On 12/21/2016 09:06 AM, Michal Hocko wrote: >>> From: Michal Hocko >>> >>> Jia He has noticed that b9f00e147f27 ("mm, page_alloc: reduce branches >>> in zone_statistics") has an unintentional side effect that remote node >>> allocation requests are accounted as NUMA_MISS rathat than NUMA_HIT and >>> NUMA_OTHER if such a request doesn't use __GFP_OTHER_NODE. There are >>> many of these potentially because the flag is used very rarely while >>> we have many users of __alloc_pages_node. >>> >>> Fix this by simply ignoring __GFP_OTHER_NODE (it can be removed in a >>> follow up patch) and treat all allocations that were satisfied from the >>> preferred zone's node as NUMA_HITS because this is the same node we >>> requested the allocation from in most cases. If this is not the local >>> node then we just account it as NUMA_OTHER rather than NUMA_LOCAL. >>> >>> One downsize would be that an allocation request for a node which is >>> outside of the mempolicy nodemask would be reported as a hit which is a >>> bit weird but that was the case before b9f00e147f27 already. >>> >>> Reported-by: Jia He >>> Fixes: b9f00e147f27 ("mm, page_alloc: reduce branches in zone_statistics") >>> Signed-off-by: Michal Hocko >> >> cbmc tells me that this patch is not equal to pre-commit b9f00e147f27 >> (in situation where __GFP_OTHER_NODE is not passed, as that's the only >> relevant scenario after your patch), which seems unintended. >> >> counter example: >> numa_node_id() == 1 >> preferred_zone on node 0 >> allocated from zone on node 1 >> >> pre-b9f00e147f27: >> allocated zone (node 1) increased NUMA_MISS and NUMA_LOCAL >> preferred zone (node 0) increased NUMA_FOREIGN >> >> (that looks correct to me) >> >> your patch: >> allocated zone (node 1) increased NUMA_MISS >> preferred zone (node 0) increased NUMA_FOREIGN >> >> i.e. it's missing NUMA_LOCAL on node 1, which is IMHO wrong as this was >> an allocation local to the CPU (albeit a MISS wrt the preferred node). > > I guess the following should fix that, right? Yes, it does. With that, you can add: Reviewed-by: Vlastimil Babka (which is a lie, since the computer did that ;) > --- > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 647e940e6921..ea60dc06d280 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2587,17 +2587,18 @@ int __isolate_free_page(struct page *page, unsigned int order) > static inline void zone_statistics(struct zone *preferred_zone, struct zone *z) > { > #ifdef CONFIG_NUMA > - if (z->node == preferred_zone->node) { > - enum zone_stat_item local_stat = NUMA_LOCAL; > + enum zone_stat_item local_stat = NUMA_LOCAL; > > + if (z->node != numa_node_id()) > + local_stat = NUMA_OTHER; > + > + if (z->node == preferred_zone->node) > __inc_zone_state(z, NUMA_HIT); > - if (z->node != numa_node_id()) > - local_stat = NUMA_OTHER; > - __inc_zone_state(z, local_stat); > - } else { > + else { > __inc_zone_state(z, NUMA_MISS); > __inc_zone_state(preferred_zone, NUMA_FOREIGN); > } > + __inc_zone_state(z, local_stat); > #endif > } > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org