From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id DD0AE6B0069 for ; Mon, 2 Jan 2017 09:46:38 -0500 (EST) Received: by mail-wm0-f72.google.com with SMTP id c85so44464862wmi.6 for ; Mon, 02 Jan 2017 06:46:38 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id b15si43966615wmf.133.2017.01.02.06.46.37 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 02 Jan 2017 06:46:37 -0800 (PST) Date: Mon, 2 Jan 2017 15:46:34 +0100 From: Michal Hocko Subject: Re: [PATCH 1/2] mm: fix remote numa hits statistics Message-ID: <20170102144634.GB18048@dhcp22.suse.cz> References: <20161221075711.GF16502@dhcp22.suse.cz> <20161221080653.29437-1-mhocko@kernel.org> <1d9e466b-dc87-eb41-113f-e7737a4bb7ef@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d9e466b-dc87-eb41-113f-e7737a4bb7ef@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: linux-mm@kvack.org, Mel Gorman , Andrew Morton , Joonsoo Kim , Jia He , Taku Izumi , Johannes Weiner 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? --- 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 } -- Michal Hocko SUSE Labs -- 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