[tip:sched/core] sched/numa: Skip nodes that are at 'hoplimit'

From: tip-bot for Srikar Dronamraju
Date: Wed Jul 25 2018 - 10:27:31 EST

Commit-ID: 0ee7e74dc0dc64d9900751d03c5c22dfdd173fb8
Gitweb: https://git.kernel.org/tip/0ee7e74dc0dc64d9900751d03c5c22dfdd173fb8
Author: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 20 Jun 2018 22:32:48 +0530
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 25 Jul 2018 11:41:07 +0200

sched/numa: Skip nodes that are at 'hoplimit'

When comparing two nodes at a distance of 'hoplimit', we should consider
nodes only up to 'hoplimit'. Currently we also consider nodes at 'oplimit'
distance too. Hence two nodes at a distance of 'hoplimit' will have same
groupweight. Fix this by skipping nodes at hoplimit.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS LAST_PATCH WITH_PATCH %CHANGE
16 25375.3 25308.6 -0.26
1 72617 72964 0.477

Running SPECjbb2005 on a 16 node machine and comparing bops/JVM
JVMS LAST_PATCH WITH_PATCH %CHANGE
8 113372 108750 -4.07684
1 177403 183115 3.21979

(numbers from v1 based on v4.17-rc5)
Testcase Time: Min Max Avg StdDev
numa01.sh Real: 478.45 565.90 515.11 30.87
numa01.sh Sys: 207.79 271.04 232.94 21.33
numa01.sh User: 39763.93 47303.12 43210.73 2644.86
numa02.sh Real: 60.00 61.46 60.78 0.49
numa02.sh Sys: 15.71 25.31 20.69 3.42
numa02.sh User: 5175.92 5265.86 5235.97 32.82
numa03.sh Real: 776.42 834.85 806.01 23.22
numa03.sh Sys: 114.43 128.75 121.65 5.49
numa03.sh User: 60773.93 64855.25 62616.91 1576.39
numa04.sh Real: 456.93 511.95 482.91 20.88
numa04.sh Sys: 178.09 460.89 356.86 94.58
numa04.sh User: 36312.09 42553.24 39623.21 2247.96
numa05.sh Real: 393.98 493.48 436.61 35.59
numa05.sh Sys: 164.49 329.15 265.87 61.78
numa05.sh User: 33182.65 36654.53 35074.51 1187.71

Testcase Time: Min Max Avg StdDev %Change
numa01.sh Real: 414.64 819.20 556.08 147.70 -7.36%
numa01.sh Sys: 77.52 205.04 139.40 52.05 67.10%
numa01.sh User: 37043.24 61757.88 45517.48 9290.38 -5.06%
numa02.sh Real: 60.80 63.32 61.63 0.88 -1.37%
numa02.sh Sys: 17.35 39.37 25.71 7.33 -19.5%
numa02.sh User: 5213.79 5374.73 5268.90 55.09 -0.62%
numa03.sh Real: 780.09 948.64 831.43 63.02 -3.05%
numa03.sh Sys: 104.96 136.92 116.31 11.34 4.591%
numa03.sh User: 60465.42 73339.78 64368.03 4700.14 -2.72%
numa04.sh Real: 412.60 681.92 521.29 96.64 -7.36%
numa04.sh Sys: 210.32 314.10 251.77 37.71 41.74%
numa04.sh User: 34026.38 45581.20 38534.49 4198.53 2.825%
numa05.sh Real: 394.79 439.63 411.35 16.87 6.140%
numa05.sh Sys: 238.32 330.09 292.31 38.32 -9.04%
numa05.sh User: 33456.45 34876.07 34138.62 609.45 2.741%

While there is a regression with this change, this change is needed from a
correctness perspective. Also it helps consolidation as seen from perf bench
output.

Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1529514181-9842-8-git-send-email-srikar@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a10c4f8f47e8..e5f39e8dfe53 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1312,7 +1312,7 @@ static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
* of each group. Skip other nodes.
*/
if (sched_numa_topology_type == NUMA_BACKPLANE &&
- dist > maxdist)
+ dist >= maxdist)
continue;

/* Add up the faults from nearby nodes. */