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Message-ID: <f6dc1652-bc39-0b12-4b6b-29a2f9cd8484@amd.com>
Date: Fri, 25 Aug 2023 15:41:08 +0530
From: Swapnil Sapkal <Swapnil.Sapkal@....com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Juri Lelli <juri.lelli@...hat.com>,
Aaron Lu <aaron.lu@...el.com>,
Julien Desfossez <jdesfossez@...italocean.com>, x86@...nel.org
Subject: Re: [RFC PATCH v3 0/3] sched: Skip queued wakeups only when L2 is
shared
Hello Mathieu,
On 8/22/2023 5:01 PM, Mathieu Desnoyers wrote:
> This series improves performance of scheduler wakeups on large systems
> by skipping queued wakeups only when CPUs share their L2 cache, rather
> than when they share their LLC.
>
> The speedup mainly reproduces on workloads which have at least *some*
> idle time (because it significantly increases the number of migrations,
> and thus remote wakeups), *and* it needs to have a sufficient load to
> cause contention on the runqueue locks.
>
> Feedback is welcome,
I ran some micro-benchmarks as part of testing this series. Here are the
observations:
- Hackbench shows improvement with this patch and Aaron's patch with
6.5-rc1 kernel as the baseline.
- tbench and netperf shows shows some dip in performance with highly
overloaded case.
- Other micro-benchmarks shows more or less similar performance with
these patches.
o System Details
- 4th Generation EPYC System
- 2 x 128C/256T
- NPS1 mode
o Kernels
base: 6.5.0-rc1
base + mathieu-queued-wakeup: 6.5.0-rc1 + Mathieu's patches [1]
base + aaron-tg-load-avg: 6.5.0-rc1 + Aaron's patch [2]
base + queued-wakeup + tg-load-avg: 6.5.0-rc1 + Mathieu's patches [1] + Aaron's patch [2]
[References]
[1] "sched: Skip queued wakeups only when L2 is shared"
(https://lore.kernel.org/all/20230822113133.643238-1-mathieu.desnoyers@efficios.com/)
[2] "Reduce cost of accessing tg->load_avg"
(https://lore.kernel.org/lkml/20230823060832.454842-1-aaron.lu@intel.com/)
==================================================================
Test : hackbench
Units : Time in seconds
Interpretation: Lower is better
Statistic : AMean
==================================================================
Test: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1-groups: 22.15 (0.00 pct) 22.46 (-1.39 pct) 22.35 (-0.90 pct) 21.20 (4.28 pct)
2-groups: 22.76 (0.00 pct) 21.78 (4.30 pct) 22.60 (0.70 pct) 21.90 (3.77 pct)
4-groups: 22.12 (0.00 pct) 22.02 (0.45 pct) 22.22 (-0.45 pct) 21.94 (0.81 pct)
8-groups: 24.80 (0.00 pct) 22.36 (9.83 pct) 22.99 (7.29 pct) 22.00 (11.29 pct)
16-groups: 31.09 (0.00 pct) 21.56 (30.65 pct) 22.13 (28.81 pct) 20.60 (33.74 pct)
==================================================================
Test : tbench
Units : Throughput
Interpretation: Higher is better
Statistic : AMean
==================================================================
Clients: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1 261.49 (0.00 pct) 261.18 (-0.11 pct) 262.29 (0.30 pct) 257.80 (-1.41 pct)
2 514.08 (0.00 pct) 521.30 (1.40 pct) 517.66 (0.69 pct) 510.96 (-0.60 pct)
4 1002.51 (0.00 pct) 988.81 (-1.36 pct) 995.04 (-0.74 pct) 987.74 (-1.47 pct)
8 1978.74 (0.00 pct) 1966.60 (-0.61 pct) 1991.85 (0.66 pct) 1941.39 (-1.88 pct)
16 3864.14 (0.00 pct) 3952.03 (2.27 pct) 3914.80 (1.31 pct) 3873.88 (0.25 pct)
32 7473.19 (0.00 pct) 7602.38 (1.72 pct) 7585.94 (1.50 pct) 7423.44 (-0.66 pct)
64 14335.10 (0.00 pct) 14313.17 (-0.15 pct) 14474.67 (0.97 pct) 14030.63 (-2.12 pct)
128 27275.73 (0.00 pct) 25176.80 (-7.69 pct) 28066.53 (2.89 pct) 25045.53 (-8.17 pct)
256 41688.17 (0.00 pct) 44373.40 (6.44 pct) 43779.37 (5.01 pct) 41427.00 (-0.62 pct)
512 137481.33 (0.00 pct) 136466.67 (-0.73 pct) 134824.00 (-1.93 pct) 141280.00 (2.76 pct)
1024 140534.00 (0.00 pct) 141916.33 (0.98 pct) 137008.33 (-2.50 pct) 126319.33 (-10.11 pct)
2048 145378.00 (0.00 pct) 145479.33 (0.06 pct) 138763.67 (-4.54 pct) 124471.00 (-14.38 pct)
==================================================================
Test : netperf
Units : Througput
Interpretation: Higher is better
Statistic : AMean
==================================================================
6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1-clients: 59642.88 (0.00 pct) 61647.37 (3.36 pct) 61186.24 (2.58 pct) 59099.11 (-0.91 pct)
2-clients: 59349.65 (0.00 pct) 60896.01 (2.60 pct) 60582.49 (2.07 pct) 62738.47 (5.70 pct)
4-clients: 59197.37 (0.00 pct) 60457.29 (2.12 pct) 63042.52 (6.49 pct) 60879.58 (2.84 pct)
8-clients: 61977.66 (0.00 pct) 60389.92 (-2.56 pct) 62078.15 (0.16 pct) 60314.65 (-2.68 pct)
16-clients: 61518.83 (0.00 pct) 61143.51 (-0.61 pct) 60946.08 (-0.93 pct) 59388.78 (-3.46 pct)
32-clients: 58230.81 (0.00 pct) 58653.20 (0.72 pct) 58594.14 (0.62 pct) 58188.52 (-0.07 pct)
64-clients: 58050.92 (0.00 pct) 57834.55 (-0.37 pct) 58183.51 (0.22 pct) 57565.75 (-0.83 pct)
128-clients: 54324.55 (0.00 pct) 54385.60 (0.11 pct) 54913.43 (1.08 pct) 53917.11 (-0.75 pct)
256-clients: 70155.29 (0.00 pct) 69390.68 (-1.08 pct) 70097.50 (-0.08 pct) 64410.66 (-8.18 pct)
512-clients: 61511.77 (0.00 pct) 61480.99 (-0.05 pct) 54493.82 (-11.40 pct) 46227.05 (-24.84 pct)
==================================================================
Test : stream-10
Units : Bandwidth, MB/s
Interpretation: Higher is better
Statistic : HMean
==================================================================
Test: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
Copy: 353336.76 (0.00 pct) 352956.36 (-0.10 pct) 349583.67 (-1.06 pct) 351152.80 (-0.61 pct)
Scale: 353474.88 (0.00 pct) 354582.35 (0.31 pct) 350543.75 (-0.82 pct) 353275.74 (-0.05 pct)
Add: 371984.24 (0.00 pct) 372824.87 (0.22 pct) 369173.72 (-0.75 pct) 370483.63 (-0.40 pct)
Triad: 372625.41 (0.00 pct) 278389.62 (-25.28 pct) 369504.06 (-0.83 pct) 369070.11 (-0.95 pct)
==================================================================
Test : stream-100
Units : Bandwidth, MB/s
Interpretation: Higher is better
Statistic : HMean
==================================================================
Test: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
Copy: 353476.35 (0.00 pct) 354954.50 (0.41 pct) 354614.56 (0.32 pct) 353512.71 (0.01 pct)
Scale: 353214.73 (0.00 pct) 354884.12 (0.47 pct) 355841.17 (0.74 pct) 353220.53 (0.00 pct)
Add: 370755.48 (0.00 pct) 372292.72 (0.41 pct) 375307.35 (1.22 pct) 369917.77 (-0.22 pct)
Triad: 370652.02 (0.00 pct) 372732.11 (0.56 pct) 375718.85 (1.36 pct) 369926.26 (-0.19 pct)
==================================================================
Test : schbench (old)
Units : 99th percentile latency in us
Interpretation: Lower is better
Statistic : Median
==================================================================
#workers: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1: 56.00 (0.00 pct) 58.00 (-3.57 pct) 60.00 (-7.14 pct) 60.00 (-7.14 pct)
2: 61.00 (0.00 pct) 56.00 (8.19 pct) 59.00 (3.27 pct) 60.00 (1.63 pct)
4: 64.00 (0.00 pct) 62.00 (3.12 pct) 66.00 (-3.12 pct) 64.00 (0.00 pct)
8: 96.00 (0.00 pct) 78.00 (18.75 pct) 76.00 (20.83 pct) 93.00 (3.12 pct)
16: 98.00 (0.00 pct) 95.00 (3.06 pct) 98.00 (0.00 pct) 95.00 (3.06 pct)
32: 137.00 (0.00 pct) 144.00 (-5.10 pct) 133.00 (2.91 pct) 130.00 (5.10 pct)
64: 206.00 (0.00 pct) 210.00 (-1.94 pct) 200.00 (2.91 pct) 217.00 (-5.33 pct)
128: 348.00 (0.00 pct) 347.00 (0.28 pct) 413.00 (-18.67 pct) 366.00 (-5.17 pct)
256: 679.00 (0.00 pct) 669.00 (1.47 pct) 669.00 (1.47 pct) 675.00 (0.58 pct)
512: 1366.00 (0.00 pct) 1366.00 (0.00 pct) 1442.00 (-5.56 pct) 1430.00 (-4.68 pct)
==================================================================
Test : schbench (new)
Units : 99th percentile latency in us
Interpretation: Lower is better
Statistic : Median
==================================================================
Metric: wakeup_lat_summary
#workers: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1: 15.00 (0.00 pct) 15.00 (0.00 pct) 16.00 (-6.66 pct) 17.00 (-13.33 pct)
2: 16.00 (0.00 pct) 16.00 (0.00 pct) 17.00 (-6.25 pct) 17.00 (-6.25 pct)
4: 17.00 (0.00 pct) 17.00 (0.00 pct) 15.00 (11.76 pct) 17.00 (0.00 pct)
8: 11.00 (0.00 pct) 13.00 (-18.18 pct) 11.00 (0.00 pct) 11.00 (0.00 pct)
16: 11.00 (0.00 pct) 11.00 (0.00 pct) 10.00 (9.09 pct) 9.00 (18.18 pct)
32: 11.00 (0.00 pct) 11.00 (0.00 pct) 11.00 (0.00 pct) 11.00 (0.00 pct)
64: 10.00 (0.00 pct) 11.00 (-10.00 pct) 10.00 (0.00 pct) 10.00 (0.00 pct)
128: 11.00 (0.00 pct) 12.00 (-9.09 pct) 12.00 (-9.09 pct) 11.00 (0.00 pct)
256: 117.00 (0.00 pct) 162.00 (-38.46 pct) 90.00 (23.07 pct) 103.00 (11.96 pct)
512: 22496.00 (0.00 pct) 21664.00 (3.69 pct) 22368.00 (0.56 pct) 21408.00 (4.83 pct)
Metric: request_lat_summary
#workers: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1: 6872.00 (0.00 pct) 6872.00 (0.00 pct) 6792.00 (1.16 pct) 6856.00 (0.23 pct)
2: 6824.00 (0.00 pct) 6824.00 (0.00 pct) 6872.00 (-0.70 pct) 6856.00 (-0.46 pct)
4: 6824.00 (0.00 pct) 6808.00 (0.23 pct) 6872.00 (-0.70 pct) 6824.00 (0.00 pct)
8: 6824.00 (0.00 pct) 6824.00 (0.00 pct) 6872.00 (-0.70 pct) 6824.00 (0.00 pct)
16: 6824.00 (0.00 pct) 6840.00 (-0.23 pct) 6872.00 (-0.70 pct) 6840.00 (-0.23 pct)
32: 6840.00 (0.00 pct) 6840.00 (0.00 pct) 6888.00 (-0.70 pct) 6856.00 (-0.23 pct)
64: 6840.00 (0.00 pct) 6872.00 (-0.46 pct) 6888.00 (-0.70 pct) 6872.00 (-0.46 pct)
128: 12272.00 (0.00 pct) 12784.00 (-4.17 pct) 13200.00 (-7.56 pct) 12016.00 (2.08 pct)
256: 13328.00 (0.00 pct) 13392.00 (-0.48 pct) 13712.00 (-2.88 pct) 13552.00 (-1.68 pct)
512: 88832.00 (0.00 pct) 86400.00 (2.73 pct) 88192.00 (0.72 pct) 85632.00 (3.60 pct)
Metric: rps_summary
#workers: 6.5.0-rc1 (base) base + mathieu-queued-wakeup base + aaron-tg-load-avg base + queued-wakeup + tg-load-avg
1: 297.00 (0.00 pct) 297.00 (0.00 pct) 297.00 (0.00 pct) 299.00 (-0.67 pct)
2: 601.00 (0.00 pct) 603.00 (-0.33 pct) 595.00 (0.99 pct) 601.00 (0.00 pct)
4: 1206.00 (0.00 pct) 1206.00 (0.00 pct) 1190.00 (1.32 pct) 1206.00 (0.00 pct)
8: 2412.00 (0.00 pct) 2412.00 (0.00 pct) 2396.00 (0.66 pct) 2420.00 (-0.33 pct)
16: 4840.00 (0.00 pct) 4824.00 (0.33 pct) 4792.00 (0.99 pct) 4840.00 (0.00 pct)
32: 9648.00 (0.00 pct) 9648.00 (0.00 pct) 9584.00 (0.66 pct) 9680.00 (-0.33 pct)
64: 19360.00 (0.00 pct) 19296.00 (0.33 pct) 19168.00 (0.99 pct) 19296.00 (0.33 pct)
128: 37952.00 (0.00 pct) 35264.00 (7.08 pct) 36672.00 (3.37 pct) 38080.00 (-0.33 pct)
256: 41408.00 (0.00 pct) 41536.00 (-0.30 pct) 39744.00 (4.01 pct) 40896.00 (1.23 pct)
512: 36288.00 (0.00 pct) 36800.00 (-1.41 pct) 35264.00 (2.82 pct) 35776.00 (1.41 pct)
Tested-by: Swapnil Sapkal <Swapnil.Sapkal@....com>
>
> Thanks,
>
> Mathieu
>
> Mathieu Desnoyers (3):
> sched: Rename cpus_share_cache to cpus_share_llc
> sched: Introduce cpus_share_l2c (v3)
> sched: ttwu_queue_cond: skip queued wakeups across different l2 caches
>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Swapnil Sapkal <Swapnil.Sapkal@....com>
> Cc: Aaron Lu <aaron.lu@...el.com>
> Cc: Julien Desfossez <jdesfossez@...italocean.com>
> Cc: x86@...nel.org
>
> block/blk-mq.c | 2 +-
> include/linux/sched/topology.h | 10 ++++++++--
> kernel/sched/core.c | 14 +++++++++++---
> kernel/sched/fair.c | 8 ++++----
> kernel/sched/sched.h | 2 ++
> kernel/sched/topology.c | 32 +++++++++++++++++++++++++++++---
> 6 files changed, 55 insertions(+), 13 deletions(-)
>
--
Thanks and Regards,
Swapnil
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