From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f200.google.com (mail-wj0-f200.google.com [209.85.210.200]) by kanga.kvack.org (Postfix) with ESMTP id 4F66B6B0069 for ; Mon, 2 Jan 2017 09:16:27 -0500 (EST) Received: by mail-wj0-f200.google.com with SMTP id xr1so107641650wjb.7 for ; Mon, 02 Jan 2017 06:16:27 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 203si69645370wms.92.2017.01.02.06.16.25 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 02 Jan 2017 06:16:25 -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> From: Vlastimil Babka Message-ID: <1d9e466b-dc87-eb41-113f-e7737a4bb7ef@suse.cz> Date: Mon, 2 Jan 2017 15:16:23 +0100 MIME-Version: 1.0 In-Reply-To: <20161221080653.29437-1-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , linux-mm@kvack.org Cc: Mel Gorman , Andrew Morton , Joonsoo Kim , Jia He , Taku Izumi , Johannes Weiner , Michal Hocko Archived-At: List-Archive: List-Post: 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). Vlastimil > --- > mm/page_alloc.c | 16 ++++------------ > 1 file changed, 4 insertions(+), 12 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index f6d5b73e1d7c..506946a902c5 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2583,25 +2583,17 @@ int __isolate_free_page(struct page *page, unsigned int order) > * Update NUMA hit/miss statistics > * > * Must be called with interrupts disabled. > - * > - * When __GFP_OTHER_NODE is set assume the node of the preferred > - * zone is the local node. This is useful for daemons who allocate > - * memory on behalf of other processes. > */ > static inline void zone_statistics(struct zone *preferred_zone, struct zone *z, > gfp_t flags) > { > #ifdef CONFIG_NUMA > - int local_nid = numa_node_id(); > - enum zone_stat_item local_stat = NUMA_LOCAL; > - > - if (unlikely(flags & __GFP_OTHER_NODE)) { > - local_stat = NUMA_OTHER; > - local_nid = preferred_zone->node; > - } > + if (z->node == preferred_zone->node) { > + enum zone_stat_item local_stat = NUMA_LOCAL; > > - if (z->node == local_nid) { > __inc_zone_state(z, NUMA_HIT); > + if (z->node != numa_node_id()) > + local_stat = NUMA_OTHER; > __inc_zone_state(z, local_stat); > } else { > __inc_zone_state(z, NUMA_MISS); > -- 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