All of lore.kernel.org
 help / color / mirror / Atom feed
From: Mel Gorman <mgorman@techsingularity.net>
To: Jia He <hejianet@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Taku Izumi <izumi.taku@jp.fujitsu.com>
Subject: Re: [PATCH RFC 1/1] mm, page_alloc: fix incorrect zone_statistics data
Date: Tue, 20 Dec 2016 12:31:22 +0000	[thread overview]
Message-ID: <20161220123121.e4wgkxm2txdoxogo@techsingularity.net> (raw)
In-Reply-To: <1481522347-20393-2-git-send-email-hejianet@gmail.com>

On Mon, Dec 12, 2016 at 01:59:07PM +0800, Jia He wrote:
> In commit b9f00e147f27 ("mm, page_alloc: reduce branches in
> zone_statistics"), it reconstructed codes to reduce the branch miss rate.
> Compared with the original logic, it assumed if !(flag & __GFP_OTHER_NODE)
>  z->node would not be equal to preferred_zone->node. That seems to be
> incorrect.
> 
> Fixes: commit b9f00e147f27 ("mm, page_alloc: reduce branches in
> zone_statistics")
> 
> Signed-off-by: Jia He <hejianet@gmail.com>

This is slightly curious. It appear it would only occur if a process was
running on a node that was outside the memory policy. Can you confirm
that is the case?

If so, your patch is a a semantic curiousity because it's actually
impossible for a NUMA allocation to be local and the definition of "HIT"
is fuzzy enough to be useless.

I won't object to the patch but it makes me trust "hit" even less than I
already do for any analysis.

Note that after this mail that I'll be unavailable by mail until early
new years.

-- 
Mel Gorman
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@techsingularity.net>
To: Jia He <hejianet@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Taku Izumi <izumi.taku@jp.fujitsu.com>
Subject: Re: [PATCH RFC 1/1] mm, page_alloc: fix incorrect zone_statistics data
Date: Tue, 20 Dec 2016 12:31:22 +0000	[thread overview]
Message-ID: <20161220123121.e4wgkxm2txdoxogo@techsingularity.net> (raw)
In-Reply-To: <1481522347-20393-2-git-send-email-hejianet@gmail.com>

On Mon, Dec 12, 2016 at 01:59:07PM +0800, Jia He wrote:
> In commit b9f00e147f27 ("mm, page_alloc: reduce branches in
> zone_statistics"), it reconstructed codes to reduce the branch miss rate.
> Compared with the original logic, it assumed if !(flag & __GFP_OTHER_NODE)
>  z->node would not be equal to preferred_zone->node. That seems to be
> incorrect.
> 
> Fixes: commit b9f00e147f27 ("mm, page_alloc: reduce branches in
> zone_statistics")
> 
> Signed-off-by: Jia He <hejianet@gmail.com>

This is slightly curious. It appear it would only occur if a process was
running on a node that was outside the memory policy. Can you confirm
that is the case?

If so, your patch is a a semantic curiousity because it's actually
impossible for a NUMA allocation to be local and the definition of "HIT"
is fuzzy enough to be useless.

I won't object to the patch but it makes me trust "hit" even less than I
already do for any analysis.

Note that after this mail that I'll be unavailable by mail until early
new years.

-- 
Mel Gorman
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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  parent reply	other threads:[~2016-12-20 12:31 UTC|newest]

Thread overview: 38+ 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 ` Jia He
2016-12-12  5:59 ` [PATCH RFC 1/1] " Jia He
2016-12-12  5:59   ` Jia He
2016-12-20  9:18   ` Michal Hocko
2016-12-20  9:18     ` Michal Hocko
2016-12-20 13:10     ` Mel Gorman
2016-12-20 13:10       ` Mel Gorman
2016-12-20 13:26       ` Michal Hocko
2016-12-20 13:26         ` Michal Hocko
2016-12-20 14:28         ` Mel Gorman
2016-12-20 14:28           ` Mel Gorman
2016-12-20 14:35           ` Michal Hocko
2016-12-20 14:35             ` Michal Hocko
2016-12-20 14:49             ` Vlastimil Babka
2016-12-20 14:49               ` Vlastimil Babka
2016-12-20 14:54             ` Mel Gorman
2016-12-20 14:54               ` Mel Gorman
2016-12-21  7:57               ` Michal Hocko
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
2016-12-20 14:42           ` [PATCH RFC 1/1] mm, page_alloc: fix incorrect zone_statistics data Mel Gorman
2016-12-20 14:42             ` Mel Gorman
2016-12-20 15:13     ` Vlastimil Babka
2016-12-20 15:13       ` Vlastimil Babka
2016-12-21  3:01     ` hejianet
2016-12-21  3:01       ` hejianet
2016-12-20 12:31   ` Mel Gorman [this message]
2016-12-20 12:31     ` Mel Gorman
2016-12-21  3:07     ` hejianet
2016-12-21  3:07       ` hejianet

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=20161220123121.e4wgkxm2txdoxogo@techsingularity.net \
    --to=mgorman@techsingularity.net \
    --cc=akpm@linux-foundation.org \
    --cc=hannes@cmpxchg.org \
    --cc=hejianet@gmail.com \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=izumi.taku@jp.fujitsu.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@suse.com \
    --cc=vbabka@suse.cz \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.