From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Jirka Hladky <jhladky@redhat.com>,
Rik van Riel <riel@surriel.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 1/2] mm, numa: Remove rate-limiting of automatic numa balancing migration
Date: Tue, 2 Oct 2018 17:24:12 +0530 [thread overview]
Message-ID: <20181002115412.GA4593@linux.vnet.ibm.com> (raw)
In-Reply-To: <20181001100525.29789-2-mgorman@techsingularity.net>
* Mel Gorman <mgorman@techsingularity.net> [2018-10-01 11:05:24]:
> Rate limiting of page migrations due to automatic NUMA balancing was
> introduced to mitigate the worst-case scenario of migrating at high
> frequency due to false sharing or slowly ping-ponging between nodes.
> Since then, a lot of effort was spent on correctly identifying these
> pages and avoiding unnecessary migrations and the safety net may no longer
> be required.
>
> Jirka Hladky reported a regression in 4.17 due to a scheduler patch that
> avoids spreading STREAM tasks wide prematurely. However, once the task
> was properly placed, it delayed migrating the memory due to rate limiting.
> Increasing the limit fixed the problem for him.
>
> Currently, the limit is hard-coded and does not account for the real
> capabilities of the hardware. Even if an estimate was attempted, it would
> not properly account for the number of memory controllers and it could
> not account for the amount of bandwidth used for normal accesses. Rather
> than fudging, this patch simply eliminates the rate limiting.
>
> However, Jirka reports that a STREAM configuration using multiple
> processes achieved similar performance to 4.16. In local tests, this patch
> improved performance of STREAM relative to the baseline but it is somewhat
> machine-dependent. Most workloads show little or not performance difference
> implying that there is not a heavily reliance on the throttling mechanism
> and it is safe to remove.
>
> STREAM on 2-socket machine
> 4.19.0-rc5 4.19.0-rc5
> numab-v1r1 noratelimit-v1r1
> MB/sec copy 43298.52 ( 0.00%) 44673.38 ( 3.18%)
> MB/sec scale 30115.06 ( 0.00%) 31293.06 ( 3.91%)
> MB/sec add 32825.12 ( 0.00%) 34883.62 ( 6.27%)
> MB/sec triad 32549.52 ( 0.00%) 34906.60 ( 7.24%
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2018-10-02 11:54 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-01 10:05 [PATCH 0/2] Faster migration for automatic NUMA balancing Mel Gorman
2018-10-01 10:05 ` [PATCH 1/2] mm, numa: Remove rate-limiting of automatic numa balancing migration Mel Gorman
2018-10-01 15:39 ` Rik van Riel
2018-10-02 10:17 ` [tip:sched/urgent] mm, sched/numa: Remove rate-limiting of automatic NUMA " tip-bot for Mel Gorman
2018-10-02 11:54 ` Srikar Dronamraju [this message]
2018-10-01 10:05 ` [PATCH 2/2] mm, numa: Migrate pages to local nodes quicker early in the lifetime of a task Mel Gorman
2018-10-01 15:41 ` Rik van Riel
2018-10-02 10:17 ` [tip:sched/urgent] sched/numa: " tip-bot for Mel Gorman
2018-10-02 12:41 ` [PATCH 2/2] mm, numa: " Srikar Dronamraju
2018-10-02 13:54 ` Mel Gorman
2018-10-02 17:30 ` Srikar Dronamraju
2018-10-02 18:22 ` Mel Gorman
2018-10-03 13:15 ` Srikar Dronamraju
2018-10-03 13:07 ` Srikar Dronamraju
2018-10-03 13:21 ` Mel Gorman
2018-10-03 14:08 ` Srikar Dronamraju
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