From: Mel Gorman <mgorman@techsingularity.net>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@surriel.com>,
LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 0/4] Follow-up fixes for v4.19-rc1 NUMA balancing
Date: Fri, 7 Sep 2018 11:11:35 +0100 [thread overview]
Message-ID: <20180907101139.20760-1-mgorman@techsingularity.net> (raw)
Srikar had an automatic NUMA balancing series merged during the 4.19 window
and there some issues I missed during review that this series addresses.
Patches 1-2 are simply removing redundant code and calculations that are
never used.
Patch 3 makes the observation that we can call select_idle_sibling during
NUMA placement several times for each idle CPU on a socket. The patch
stops the search on the first idle CPU. While there is the risk that
parallel callers will stack on the same idle CPU, the current code has
the same problem.
Patch 4 is the one that needs the most examination. I believe intent of
load_too_imbalanced was to stop automatic NUMA balancing fighting the load
balancer. Unfortunately, when a machine is lightly utilised there are idle
CPUs and tasks are allowed to migrate even though the load is imbalanced.
In some cases, this limits memory bandwidth and can perform worse even if
data locality is fine. The patch corrects the condition.
If they pass review, I think it would suggest considering them a fix for
4.19 instead of deferring to 4.20.
kernel/sched/fair.c | 35 ++++++++---------------------------
1 file changed, 8 insertions(+), 27 deletions(-)
--
2.16.4
next reply other threads:[~2018-09-07 10:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 10:11 Mel Gorman [this message]
2018-09-07 10:11 ` [PATCH 1/4] sched/numa: Remove redundant numa_stats nr_running field Mel Gorman
2018-09-07 10:11 ` [PATCH 2/4] sched/numa: Remove unused calculations in update_numa_stats Mel Gorman
2018-09-07 10:11 ` [PATCH 3/4] sched/numa: Stop comparing tasks for NUMA placement after selecting an idle core Mel Gorman
2018-09-07 13:05 ` Srikar Dronamraju
2018-09-07 14:20 ` Mel Gorman
2018-09-07 10:11 ` [PATCH 4/4] sched/numa: Do not move imbalanced load purely on the basis of an idle CPU Mel Gorman
2018-09-07 11:33 ` Peter Zijlstra
2018-09-07 12:37 ` Mel Gorman
2018-09-07 12:44 ` Peter Zijlstra
2018-09-07 13:42 ` Srikar Dronamraju
2018-09-07 14:28 ` Mel Gorman
2018-09-10 9:41 ` Mel Gorman
2018-09-12 6:54 ` Srikar Dronamraju
2018-09-12 9:36 ` Peter Zijlstra
2018-09-12 10:45 ` Srikar Dronamraju
2018-09-12 9:57 ` Ingo Molnar
2018-09-12 10:27 ` Srikar Dronamraju
2018-09-12 10:57 ` Mel Gorman
2018-09-12 10:52 ` Mel Gorman
2018-09-07 11:24 ` [PATCH 0/4] Follow-up fixes for v4.19-rc1 NUMA balancing Peter Zijlstra
2018-09-07 12:29 ` Mel Gorman
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