From: Michal Hocko <mhocko@suse.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Joonsoo Kim <js1304@gmail.com>, Jia He <hejianet@gmail.com>,
Taku Izumi <izumi.taku@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 1/2] mm: fix remote numa hits statistics
Date: Mon, 2 Jan 2017 15:46:34 +0100 [thread overview]
Message-ID: <20170102144634.GB18048@dhcp22.suse.cz> (raw)
In-Reply-To: <1d9e466b-dc87-eb41-113f-e7737a4bb7ef@suse.cz>
On Mon 02-01-17 15:16:23, Vlastimil Babka wrote:
> On 12/21/2016 09:06 AM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> >
> > 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 <hejianet@gmail.com>
> > Fixes: b9f00e147f27 ("mm, page_alloc: reduce branches in zone_statistics")
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
>
> 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
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next prev parent reply other threads:[~2017-01-02 14:46 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-12 5:59 [PATCH RFC 0/1] mm, page_alloc: fix incorrect zone_statistics data Jia He
2016-12-12 5:59 ` [PATCH RFC 1/1] " Jia He
2016-12-20 9:18 ` Michal Hocko
2016-12-20 13:10 ` Mel Gorman
2016-12-20 13:26 ` Michal Hocko
2016-12-20 14:28 ` Mel Gorman
2016-12-20 14:35 ` Michal Hocko
2016-12-20 14:49 ` Vlastimil Babka
2016-12-20 14:54 ` Mel Gorman
2016-12-21 7:57 ` Michal Hocko
2016-12-21 8:06 ` [PATCH 1/2] mm: fix remote numa hits statistics Michal Hocko
2016-12-21 8:06 ` [PATCH 2/2] mm: get rid of __GFP_OTHER_NODE Michal Hocko
2017-01-02 14:18 ` Vlastimil Babka
2016-12-29 11:46 ` [PATCH 1/2] mm: fix remote numa hits statistics Mel Gorman
2016-12-29 12:28 ` Michal Hocko
2017-01-02 14:16 ` Vlastimil Babka
2017-01-02 14:46 ` Michal Hocko [this message]
2017-01-02 15:07 ` Vlastimil Babka
2016-12-20 14:42 ` [PATCH RFC 1/1] mm, page_alloc: fix incorrect zone_statistics data Mel Gorman
2016-12-20 15:13 ` Vlastimil Babka
2016-12-21 3:01 ` hejianet
2016-12-20 12:31 ` Mel Gorman
2016-12-21 3:07 ` hejianet
2017-01-02 15:30 [PATCH 0/2] numa node stats alternative fix Michal Hocko
2017-01-02 15:30 ` [PATCH 1/2] mm: fix remote numa hits statistics Michal Hocko
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