From: Vlastimil Babka <vbabka@suse.cz>
To: Michal Hocko <mhocko@suse.com>
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 16:07:05 +0100 [thread overview]
Message-ID: <cd358060-7a68-2033-8e8a-5ab188099de7@suse.cz> (raw)
In-Reply-To: <20170102144634.GB18048@dhcp22.suse.cz>
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 <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?
Yes, it does.
With that, you can add:
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
(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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-01-02 15:07 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
2017-01-02 15:07 ` Vlastimil Babka [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cd358060-7a68-2033-8e8a-5ab188099de7@suse.cz \
--to=vbabka@suse.cz \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=hejianet@gmail.com \
--cc=izumi.taku@jp.fujitsu.com \
--cc=js1304@gmail.com \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=mhocko@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).