Re: [tip: sched/core] sched/fair: Multi-LLC select_idle_sibling()

K Prateek Nayak
2023-06-16T06:35:28Z

Hello Peter,

On 6/13/2023 1:55 PM, Peter Zijlstra wrote:
> LIMIT seems to do well for the NPS1 case, but how come it falls apart
> for NPS2 ?!? that doesn't realy make sense, does it?

Including the results again with a rerun of SIS_NODE_LIMIT which I
definitely messed up last time. I'll include a small tl;dr for each
benchmark to reduce the dizziness from all the numbers :)

o System Details

Dual Socket 3rd Generation EPYC System (2 x 64C/128T)

o NPS Modes

NPS Modes are used to logically divide single socket into
multiple NUMA region.
Following is the NUMA configuration for each NPS mode on the system:

NPS1: Each socket is a NUMA node.
Total 2 NUMA nodes in the dual socket machine.

Node 0: 0-63, 128-191
Node 1: 64-127, 192-255

- 8CCX per node

NPS2: Each socket is further logically divided into 2 NUMA regions.
Total 4 NUMA nodes exist over 2 socket.

Node 0: 0-31, 128-159
Node 1: 32-63, 160-191
Node 2: 64-95, 192-223
Node 3: 96-127, 223-255

- 4 CCX per node

NPS4: Each socket is logically divided into 4 NUMA regions.
Total 8 NUMA nodes exist over 2 socket.

Node 0: 0-15, 128-143
Node 1: 16-31, 144-159
Node 2: 32-47, 160-175
Node 3: 48-63, 176-191
Node 4: 64-79, 192-207
Node 5: 80-95, 208-223
Node 6: 96-111, 223-231
Node 7: 112-127, 232-255

- 2 CCX per node

Note:

- Ideally in NPS2 and NPS4 modes SIS_NODE and SIS_NODE_LIMIT should
behave similarly.

- Ideally in NPS4 mode SIS_NODE and SIS_NODE_TOPOEXT should behave
similarly.

o Kernel Versions

- tip - tip:sched/core at commit e2a1f85bf9f5 "sched/psi:
Avoid resetting the min update period when it is
unnecessary")

- SIS_NODE - tip:sched/core + this patch

- SIS_NODE_LIMIT - tip:sched/core + this patch + nr=4 limit for SIS_NODE [1]

- SIS_NODE_TOPOEXT - tip:sched/core + this patch
+ new sched domain (Multi-Multi-Core or MMC) [2]
(MMC domain groups 2 nearby CCX.)

[1] https://lore.kernel.org/all/20230601111326.GV4253@hirez.programming.kicks-ass.net/
[2] https://lore.kernel.org/all/3402dcc4-d52f-d99f-e6ce-b435478a5a59@amd.com/

o Benchmark Results

Note: All benchmarks were run with boost enabled and C2 disabled.

~~~~~~~~~~~~~
~ hackbench ~
~~~~~~~~~~~~~

tl;dr

- Similar trend is observed for SIS_NODE and SIS_NODE_LIMIT in NPS2 and
NPS4 mode.
- Similar trend is observed for all SIS_NODE and SIS_NODE_TOPOEXT for
NPS4 mode.
- Limiting search score seem to reduce the regression seen from plain
SIS_NODE with a couple of outliers but the absolute numbers are not
far off except for 16-groups in NPS4 mode for SIS_NODE_LIMIT.

o NPS1

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1-groups: 3.92 (0.00 pct) 4.05 (-3.31 pct) 3.92 (0.00 pct) 3.77 (3.82 pct)
2-groups: 4.58 (0.00 pct) 3.84 (16.15 pct) 3.81 (16.81 pct) 4.34 (5.24 pct)
4-groups: 4.99 (0.00 pct) 3.98 (20.24 pct) 4.02 (19.43 pct) 5.01 (-0.40 pct)
8-groups: 5.67 (0.00 pct) 6.05 (-6.70 pct) 6.35 (-11.99 pct) 5.95 (-4.93 pct)
16-groups: 7.88 (0.00 pct) 10.56 (-34.01 pct) 10.07 (-27.79 pct) 8.04 (-2.03 pct)

o NPS4

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1-groups: 3.82 (0.00 pct) 3.68 (3.66 pct) 3.80 (0.52 pct) 3.74 (2.09 pct)
2-groups: 4.40 (0.00 pct) 3.61 (17.95 pct) 3.90 (11.36 pct) 4.30 (2.27 pct)
4-groups: 4.84 (0.00 pct) 3.62 (25.20 pct) 4.11 (15.08 pct) 4.97 (-2.68 pct)
8-groups: 5.45 (0.00 pct) 6.14 (-12.66 pct) 6.15 (-12.84 pct) 5.68 (-4.22 pct)
16-groups: 6.94 (0.00 pct) 8.77 (-26.36 pct) 9.51 (-37.03 pct) 7.87 (-13.40 pct)

o NPS4

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1-groups: 3.82 (0.00 pct) 3.84 (-0.52 pct) 3.83 (-0.26 pct) 3.85 (-0.78 pct)
2-groups: 4.44 (0.00 pct) 4.15 (6.53 pct) 4.25 (4.27 pct) 4.18 (5.85 pct)
4-groups: 4.86 (0.00 pct) 4.95 (-1.85 pct) 5.07 (-4.32 pct) 4.79 (1.44 pct)
8-groups: 5.42 (0.00 pct) 5.80 (-7.01 pct) 6.19 (-14.20 pct) 5.75 (-6.08 pct)
16-groups: 6.68 (0.00 pct) 9.07 (-35.77 pct) 13.80 (-106.58 pct) 8.66 (-29.64 pct)

~~~~~~~~~~~~~~~~~~
~ schbench (Old) ~
~~~~~~~~~~~~~~~~~~

tl;dr

- Similar to what was observed with hackbench with few outliers here
and there.

o NPS1

#workers: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1: 26.00 (0.00 pct) 24.00 (7.69 pct) 26.00 (0.00 pct) 20.00 (23.07 pct)
2: 27.00 (0.00 pct) 24.00 (11.11 pct) 24.00 (11.11 pct) 26.00 (3.70 pct)
4: 31.00 (0.00 pct) 28.00 (9.67 pct) 29.00 (6.45 pct) 28.00 (9.67 pct)
8: 36.00 (0.00 pct) 33.00 (8.33 pct) 34.00 (5.55 pct) 34.00 (5.55 pct)
16: 49.00 (0.00 pct) 47.00 (4.08 pct) 51.00 (-4.08 pct) 50.00 (-2.04 pct)
32: 80.00 (0.00 pct) 81.00 (-1.25 pct) 82.00 (-2.50 pct) 81.00 (-1.25 pct)
64: 169.00 (0.00 pct) 169.00 (0.00 pct) 175.00 (-3.55 pct) 177.00 (-4.73 pct)
128: 343.00 (0.00 pct) 365.00 (-6.41 pct) 361.00 (-5.24 pct) 336.00 (2.04 pct)
256: 42048.00 (0.00 pct) 35392.00 (15.82 pct) 42048.00 (0.00 pct) 48576.00 (-15.52 pct)
512: 95104.00 (0.00 pct) 88704.00 (6.72 pct) 88192.00 (7.26 pct) 89984.00 (5.38 pct)

o NPS2

#workers: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1: 23.00 (0.00 pct) 24.00 (-4.34 pct) 19.00 (17.39 pct) 21.00 (8.69 pct)
2: 24.00 (0.00 pct) 24.00 (0.00 pct) 26.00 (-8.33 pct) 28.00 (-16.66 pct)
4: 31.00 (0.00 pct) 26.00 (16.12 pct) 26.00 (16.12 pct) 29.00 (6.45 pct)
8: 41.00 (0.00 pct) 38.00 (7.31 pct) 38.00 (7.31 pct) 38.00 (7.31 pct)
16: 48.00 (0.00 pct) 49.00 (-2.08 pct) 50.00 (-4.16 pct) 53.00 (-10.41 pct)
32: 81.00 (0.00 pct) 84.00 (-3.70 pct) 80.00 (1.23 pct) 86.00 (-6.17 pct)
64: 157.00 (0.00 pct) 169.00 (-7.64 pct) 162.00 (-3.18 pct) 172.00 (-9.55 pct)
128: 386.00 (0.00 pct) 400.00 (-3.62 pct) 400.00 (-3.62 pct) 384.00 (0.51 pct)
256: 48832.00 (0.00 pct) 44480.00 (8.91 pct) 44480.00 (8.91 pct) 48576.00 (0.52 pct)
512: 92032.00 (0.00 pct) 89472.00 (2.78 pct) 88448.00 (3.89 pct) 91008.00 (1.11 pct)

o NPS4

#workers: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1: 21.00 (0.00 pct) 24.00 (-14.28 pct) 23.00 (-9.52 pct) 22.00 (-4.76 pct)
2: 28.00 (0.00 pct) 24.00 (14.28 pct) 29.00 (-3.57 pct) 28.00 (0.00 pct)
4: 32.00 (0.00 pct) 29.00 (9.37 pct) 28.00 (12.50 pct) 30.00 (6.25 pct)
8: 46.00 (0.00 pct) 43.00 (6.52 pct) 44.00 (4.34 pct) 42.00 (8.69 pct)
16: 51.00 (0.00 pct) 53.00 (-3.92 pct) 57.00 (-11.76 pct) 56.00 (-9.80 pct)
32: 82.00 (0.00 pct) 81.00 (1.21 pct) 87.00 (-6.09 pct) 83.00 (-1.21 pct)
64: 173.00 (0.00 pct) 172.00 (0.57 pct) 176.00 (-1.73 pct) 155.00 (10.40 pct)
128: 396.00 (0.00 pct) 384.00 (3.03 pct) 366.00 (7.57 pct) 386.00 (2.52 pct)
256: 48832.00 (0.00 pct) 46656.00 (4.45 pct) 47296.00 (3.14 pct) 49472.00 (-1.31 pct)
512: 95104.00 (0.00 pct) 90752.00 (4.57 pct) 91264.00 (4.03 pct) 90496.00 (4.84 pct)

~~~~~~~~~~
~ tbench ~
~~~~~~~~~~

tl;dr

- I'll rerun the datapoints marked with (^) because they are
surprisingly good for SIS_NODE and not SIS_NODE_LIMIT when both are
supposed to behave exactly same.
- IN NPS1 (marked with (*)) there is a sharp outlier at 256 clients
where larger search scope seems to be more successful as machine
becomes more overloaded (?!) I'll go check some idle stats here.

o NPS1

Clients: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1 452.49 (0.00 pct) 457.94 (1.20 pct) 455.34 (0.62 pct) 447.69 (-1.06 pct)
2 862.44 (0.00 pct) 879.99 (2.03 pct) 871.34 (1.03 pct) 855.91 (-0.75 pct)
4 1604.27 (0.00 pct) 1618.87 (0.91 pct) 1621.18 (1.05 pct) 1627.14 (1.42 pct)
8 2966.77 (0.00 pct) 3040.90 (2.49 pct) 3002.73 (1.21 pct) 2957.91 (-0.29 pct)
16 5176.70 (0.00 pct) 5292.29 (2.23 pct) 5249.57 (1.40 pct) 5241.61 (1.25 pct)
32 8205.24 (0.00 pct) 8949.12 (9.06 pct) 9006.75 (9.76 pct) 8494.17 (3.52 pct)
64 13956.71 (0.00 pct) 14461.42 (3.61 pct) 15150.47 (8.55 pct) 15045.43 (7.80 pct)
128 24005.50 (0.00 pct) 26052.75 (8.52 pct) 26570.09 (10.68 pct) 24008.73 (0.01 pct) *
256 32457.61 (0.00 pct) 21999.41 (-32.22 pct) 21635.06 (-33.34 pct) 31060.12 (-4.30 pct) *
512 34345.24 (0.00 pct) 41166.39 (19.86 pct) 35180.72 (2.43 pct) 31864.14 (-7.22 pct) *
1024 33432.92 (0.00 pct) 40900.84 (22.33 pct) 36075.90 (7.90 pct) 32006.81 (-4.26 pct)

o NPS2

Clients: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1 453.73 (0.00 pct) 451.63 (-0.46 pct) 449.92 (-0.83 pct) 453.79 (0.01 pct)
2 861.71 (0.00 pct) 857.85 (-0.44 pct) 867.28 (0.64 pct) 850.14 (-1.34 pct)
4 1599.14 (0.00 pct) 1609.30 (0.63 pct) 1601.12 (0.12 pct) 1619.10 (1.24 pct)
8 2951.03 (0.00 pct) 2944.71 (-0.21 pct) 2987.26 (1.22 pct) 2973.52 (0.76 pct)
16 5080.32 (0.00 pct) 5160.39 (1.57 pct) 5213.69 (2.62 pct) 5150.99 (1.39 pct)
32 7900.41 (0.00 pct) 8039.13 (1.75 pct) 8238.31 (4.27 pct) 7956.45 (0.70 pct)
64 14629.65 (0.00 pct) 15391.08 (5.20 pct) 14246.13 (-2.62 pct) 15410.41 (5.33 pct)
128 23155.88 (0.00 pct) 24015.45 (3.71 pct) 25187.85 (8.77 pct) 23351.35 (0.84 pct)
256 33449.57 (0.00 pct) 33571.08 (0.36 pct) 29242.15 (-12.57 pct) 32869.85 (-1.73 pct)
512 33757.47 (0.00 pct) 39872.69 (18.11 pct) ^ 33893.44 (0.40 pct) 34526.17 (2.27 pct)
1024 34823.14 (0.00 pct) 41090.15 (17.99 pct) ^ 33173.55 (-4.73 pct) 34522.97 (-0.86 pct)

o NPS4

Clients: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1 450.14 (0.00 pct) 454.46 (0.95 pct) 449.90 (-0.05 pct) 451.43 (0.28 pct)
2 863.26 (0.00 pct) 868.94 (0.65 pct) 856.32 (-0.80 pct) 866.74 (0.40 pct)
4 1618.71 (0.00 pct) 1599.13 (-1.20 pct) 1592.50 (-1.61 pct) 1610.08 (-0.53 pct)
8 2929.35 (0.00 pct) 3065.12 (4.63 pct) 3052.68 (4.21 pct) 3004.74 (2.57 pct)
16 5114.04 (0.00 pct) 5261.40 (2.88 pct) 5220.86 (2.08 pct) 5108.53 (-0.10 pct)
32 7912.18 (0.00 pct) 8926.77 (12.82 pct) 8944.70 (13.04 pct) 8214.73 (3.82 pct)
64 14424.72 (0.00 pct) 14853.61 (2.97 pct) 14531.64 (0.74 pct) 14430.17 (0.03 pct)
128 23614.97 (0.00 pct) 24506.73 (3.77 pct) 25404.57 (7.57 pct) 23296.38 (-1.34 pct)
256 34365.13 (0.00 pct) 35538.42 (3.41 pct) 33123.21 (-3.61 pct) 31009.12 (-9.76 pct)
512 34215.50 (0.00 pct) 36017.49 (5.26 pct) 34398.11 (0.53 pct) 33262.55 (-2.78 pct)
1024 35421.90 (0.00 pct) 35193.81 (-0.64 pct) 36448.71 (2.89 pct) 32795.86 (-7.41 pct) *

~~~~~~~~~~
~ stream ~
~~~~~~~~~~

tl;dr

- Ideally nothing should change here since we are only running 16
STREAM threads on such a large system however in NPS4, STREAM does
not seem to be happy. (I'll go check whether it is indeed SIS_NODE)

- 10 Runs

o NPS1

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Copy: 271317.35 (0.00 pct) 292440.22 (7.78 pct) 241027.63 (-11.16 pct) 287277.25 (5.88 pct)
Scale: 205533.77 (0.00 pct) 203362.60 (-1.05 pct) 202615.73 (-1.41 pct) 205206.26 (-0.15 pct)
Add: 221624.62 (0.00 pct) 225850.83 (1.90 pct) 212399.58 (-4.16 pct) 229774.48 (3.67 pct)
Triad: 228500.68 (0.00 pct) 225885.25 (-1.14 pct) 213445.64 (-6.58 pct) 240041.53 (5.05 pct)

o NPS2

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Copy: 277761.29 (0.00 pct) 301816.34 (8.66 pct) 283260.62 (1.97 pct) 308218.80 (10.96 pct)
Scale: 215193.83 (0.00 pct) 212522.72 (-1.24 pct) 215479.38 (0.13 pct) 205678.94 (-4.42 pct)
Add: 242725.75 (0.00 pct) 242695.13 (-0.01 pct) 240395.33 (-0.96 pct) 238089.46 (-1.91 pct)
Triad: 237253.44 (0.00 pct) 250618.57 (5.63 pct) 239077.27 (0.76 pct) 249652.73 (5.22 pct)

o NPS4

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Copy: 273307.14 (0.00 pct) 255091.78 (-6.66 pct) 255965.91 (-6.34 pct) 262007.26 (-4.13 pct)
Scale: 235715.23 (0.00 pct) 222018.36 (-5.81 pct) 223368.73 (-5.23 pct) 222282.64 (-5.69 pct)
Add: 244500.40 (0.00 pct) 230468.21 (-5.73 pct) 223901.86 (-8.42 pct) 227146.80 (-7.09 pct)
Triad: 250600.04 (0.00 pct) 236229.50 (-5.73 pct) 221054.69 (-11.78 pct) 231772.02 (-7.51 pct)

- 100 Runs

o NPS1

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Copy: 317381.65 (0.00 pct) 318827.08 (0.45 pct) 316606.07 (-0.24 pct) 318922.96 (0.48 pct)
Scale: 214145.00 (0.00 pct) 206213.69 (-3.70 pct) 216937.82 (1.30 pct) 210384.47 (-1.75 pct)
Add: 239243.29 (0.00 pct) 229791.67 (-3.95 pct) 243660.76 (1.84 pct) 236659.48 (-1.07 pct)
Triad: 249477.76 (0.00 pct) 236843.06 (-5.06 pct) 237186.61 (-4.92 pct) 235990.67 (-5.40 pct)

o NPS2

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Copy: 318082.10 (0.00 pct) 322844.91 (1.49 pct) 317697.43 (-0.12 pct) 322495.84 (1.38 pct)
Scale: 219338.56 (0.00 pct) 218139.90 (-0.54 pct) 220850.47 (0.68 pct) 221040.27 (0.77 pct)
Add: 248118.20 (0.00 pct) 249826.98 (0.68 pct) 249156.94 (0.41 pct) 253006.79 (1.97 pct)
Triad: 247088.55 (0.00 pct) 260488.38 (5.42 pct) 255260.30 (3.30 pct) 249081.33 (0.80 pct)

o NPS4

Test: tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Copy: 345396.19 (0.00 pct) 343675.74 (-0.49 pct) 338130.49 (-2.10 pct) 334677.55 (-3.10 pct)
Scale: 241521.63 (0.00 pct) 231494.70 (-4.15 pct) 239206.00 (-0.95 pct) 229159.01 (-5.11 pct)
Add: 261157.86 (0.00 pct) 249663.86 (-4.40 pct) 255752.77 (-2.06 pct) 242257.98 (-7.23 pct)
Triad: 267804.99 (0.00 pct) 263071.00 (-1.76 pct) 253672.27 (-5.27 pct) 256978.50 (-4.04 pct)

~~~~~~~~~~~
~ netperf ~
~~~~~~~~~~~

tl;dr

- Similar trend as hackbench with a few outliers.

o NPS1

tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1-clients: 102839.97 (0.00 pct) 103540.33 (0.68 pct) 102890.49 (0.04 pct) 103271.77 (0.41 pct)
2-clients: 98428.08 (0.00 pct) 100431.67 (2.03 pct) 100804.93 (2.41 pct) 100417.11 (2.02 pct)
4-clients: 92298.45 (0.00 pct) 94800.51 (2.71 pct) 94137.00 (1.99 pct) 94981.10 (2.90 pct)
8-clients: 85618.41 (0.00 pct) 89130.14 (4.10 pct) 85573.71 (-0.05 pct) 88284.61 (3.11 pct)
16-clients: 78722.18 (0.00 pct) 79715.38 (1.26 pct) 79422.52 (0.88 pct) 78980.88 (0.32 pct)
32-clients: 73610.75 (0.00 pct) 72801.41 (-1.09 pct) 74763.95 (1.56 pct) 75077.55 (1.99 pct)
64-clients: 55285.07 (0.00 pct) 56184.38 (1.62 pct) 58976.82 (6.67 pct) 60689.05 (9.77 pct)
128-clients: 31176.92 (0.00 pct) 32830.06 (5.30 pct) 39403.20 (26.38 pct) 35638.50 (14.31 pct)
256-clients: 20011.44 (0.00 pct) 15135.39 (-24.36 pct) 17117.22 (-14.46 pct) 18219.29 (-8.95 pct)
512-clients: 10012.28 (0.00 pct) 9726.37 (-2.85 pct) 10492.91 (4.80 pct) 9395.51 (-6.16 pct)

o NPS2

tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1-clients: 103105.55 (0.00 pct) 101582.75 (-1.47 pct) 101709.57 (-1.35 pct) 102233.63 (-0.84 pct)
2-clients: 98720.29 (0.00 pct) 98537.46 (-0.18 pct) 98469.37 (-0.25 pct) 99211.39 (0.49 pct)
4-clients: 92289.39 (0.00 pct) 94332.45 (2.21 pct) 95033.41 (2.97 pct) 93321.77 (1.11 pct)
8-clients: 84998.63 (0.00 pct) 87180.90 (2.56 pct) 88343.42 (3.93 pct) 86076.75 (1.26 pct)
16-clients: 76395.81 (0.00 pct) 80017.06 (4.74 pct) 79511.47 (4.07 pct) 75090.85 (-1.70 pct)
32-clients: 71110.89 (0.00 pct) 69445.86 (-2.34 pct) 67564.76 (-4.98 pct) 66885.99 (-5.94 pct)
64-clients: 49526.21 (0.00 pct) 50004.13 (0.96 pct) 53450.34 (7.92 pct) 51100.52 (3.17 pct)
128-clients: 27917.51 (0.00 pct) 30581.70 (9.54 pct) 32451.97 (16.24 pct) 33477.65 (19.91 pct)
256-clients: 20067.17 (0.00 pct) 26002.42 (29.57 pct) 25011.83 (24.64 pct) 18144.96 (-9.57 pct)

o NPS4

tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1-clients: 102139.49 (0.00 pct) 103578.02 (1.40 pct) 103036.47 (0.87 pct) 101656.07 (-0.47 pct)
2-clients: 98259.53 (0.00 pct) 99336.70 (1.09 pct) 99442.86 (1.20 pct) 98812.86 (0.56 pct)
4-clients: 91576.79 (0.00 pct) 95278.30 (4.04 pct) 94412.90 (3.09 pct) 93848.94 (2.48 pct)
8-clients: 84742.30 (0.00 pct) 89005.65 (5.03 pct) 86045.25 (1.53 pct) 86709.29 (2.32 pct)
16-clients: 79540.75 (0.00 pct) 85478.97 (7.46 pct) 81959.57 (3.04 pct) 81016.24 (1.85 pct)
32-clients: 71166.14 (0.00 pct) 74254.01 (4.33 pct) 71476.02 (0.43 pct) 71391.62 (0.31 pct)
64-clients: 51763.24 (0.00 pct) 52565.56 (1.54 pct) 50651.09 (-2.14 pct) 52472.91 (1.37 pct)
128-clients: 27829.29 (0.00 pct) 35774.61 (28.55 pct) 35541.25 (27.71 pct) 34564.10 (24.20 pct)
256-clients: 24185.37 (0.00 pct) 27215.35 (12.52 pct) 31619.39 (30.73 pct) 24937.66 (3.11 pct)

~~~~~~~~~~~~~~~~
~ ycsb-mongodb ~
~~~~~~~~~~~~~~~~

tl;dr

- SIS_NODE_LIMIT shows good improvements in NPS1 mode. Other modes
are more or less similar.

o NPS1

tip: 131070.33 (var: 2.84%)
SIS_NODE: 131070.33 (var: 2.84%) (0.00%)
SIS_NODE_LIMIT: 137525.00 (var: 1.24%) (4.92%)
SIS_NODE_TOPOEXT: 133529.67 (var: 0.98%) (1.87%)

o NPS2

tip: 133693.67 (var: 1.69%)
SIS_NODE: 134173.00 (var: 4.07%) (0.35%)
SIS_NODE_LIMIT: 134068.33 (var: 2.10%) (0.28%)
SIS_NODE_TOPOEXT: 133747.33 (var: 2.49%) (0.04%)

o NPS4

tip: 132913.67 (var: 1.97%)
SIS_NODE: 133697.33 (var: 1.69%) (0.58%)
SIS_NODE_LIMIT: 133545.33 (var: 1.03%) (0.47%)
SIS_NODE_TOPOEXT: 133426.67 (var: 3.60%) (0.38%)

~~~~~~~~~~~~~
~ unixbench ~
~~~~~~~~~~~~~

tl;dr

- unixbench-syscall-512 in NPS1 and NPS2 seems to be the only gains
while others stay more or less the same with few outliers as
usual.

o NPS1

kernel tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Hmean unixbench-dhry2reg-1 41322625.19 ( 0.00%) 41224388.33 ( -0.24%) 41064084.38 ( -0.63%) 41222168.97 ( -0.24%)
Hmean unixbench-dhry2reg-512 6252491108.60 ( 0.00%) 6240160851.68 ( -0.20%) 6245401623.65 ( -0.11%) 6259553403.67 ( 0.11%)
Amean unixbench-syscall-1 2501398.27 ( 0.00%) 2577323.43 * -3.04%* 2555415.40 * -2.16%* 2541279.77 * -1.59%*
Amean unixbench-syscall-512 8120524.00 ( 0.00%) 7512955.87 * 7.48%* 7443914.67 * 8.33%* 7477129.17 * 7.92%*
Hmean unixbench-pipe-1 2359346.02 ( 0.00%) 2392308.62 * 1.40%* 2387202.32 * 1.18%* 2334146.94 * -1.07%*
Hmean unixbench-pipe-512 338790322.61 ( 0.00%) 337711432.92 ( -0.32%) 337228635.73 * -0.46%* 339008490.26 ( 0.06%)
Hmean unixbench-spawn-1 4261.52 ( 0.00%) 4164.90 ( -2.27%) 4351.26 ( 2.11%) 5111.16 * 19.94%*
Hmean unixbench-spawn-512 64328.93 ( 0.00%) 62257.64 * -3.22%* 63966.41 ( -0.56%) 63291.18 * -1.61%*
Hmean unixbench-execl-1 3677.73 ( 0.00%) 3652.08 ( -0.70%) 3599.76 * -2.12%* 3671.98 ( -0.16%)
Hmean unixbench-execl-512 11984.83 ( 0.00%) 13585.65 * 13.36%* 13521.41 * 12.82%* 12306.01 ( 2.68%)

o NPS2

kernel tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Hmean unixbench-dhry2reg-1 41311787.29 ( 0.00%) 41412946.27 ( 0.24%) 41305805.50 ( -0.01%) 41371003.93 ( 0.14%)
Hmean unixbench-dhry2reg-512 6243873272.76 ( 0.00%) 6256893083.32 ( 0.21%) 6246099911.20 ( 0.04%) 6235047089.83 ( -0.14%)
Amean unixbench-syscall-1 2503190.70 ( 0.00%) 2576854.30 * -2.94%* 2554603.93 * -2.05%* 2540298.77 * -1.48%*
Amean unixbench-syscall-512 8012388.13 ( 0.00%) 7503196.87 * 6.36%* 8076005.50 * -0.79%* 7495117.73 * 6.46%*
Hmean unixbench-pipe-1 2340486.25 ( 0.00%) 2388946.63 ( 2.07%) 2397554.45 * 2.44%* 2360277.30 ( 0.85%)
Hmean unixbench-pipe-512 338965319.79 ( 0.00%) 337225630.07 ( -0.51%) 336766051.70 * -0.65%* 336939353.18 * -0.60%*
Hmean unixbench-spawn-1 5241.83 ( 0.00%) 5246.00 ( 0.08%) 5248.48 ( 0.13%) 4967.96 * -5.22%*
Hmean unixbench-spawn-512 65799.86 ( 0.00%) 64817.15 * -1.49%* 64569.20 * -1.87%* 66820.63 * 1.55%*
Hmean unixbench-execl-1 3670.65 ( 0.00%) 3622.36 * -1.32%* 3633.71 ( -1.01%) 3660.08 ( -0.29%)
Hmean unixbench-execl-512 13682.00 ( 0.00%) 13699.90 ( 0.13%) 13969.40 ( 2.10%) 12960.11 ( -5.28%)

o NPS4

kernel tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
Hmean unixbench-dhry2reg-1 41025577.99 ( 0.00%) 40879469.78 ( -0.36%) 41209188.37 * 0.45%* 41260407.54 ( 0.57%)
Hmean unixbench-dhry2reg-512 6255568261.91 ( 0.00%) 6258326086.80 ( 0.04%) 6256509267.44 ( 0.02%) 6259088809.43 ( 0.06%)
Amean unixbench-syscall-1 2507165.37 ( 0.00%) 2579108.77 * -2.87%* 2554902.63 * -1.90%* 2517574.40 ( -0.42%)
Amean unixbench-syscall-512 7458476.50 ( 0.00%) 7502528.67 * -0.59%* 7587645.17 * -1.73%* 7580369.27 * -1.63%*
Hmean unixbench-pipe-1 2369301.21 ( 0.00%) 2392905.29 * 1.00%* 2383343.22 ( 0.59%) 2347814.20 ( -0.91%)
Hmean unixbench-pipe-512 340299405.72 ( 0.00%) 339139980.01 * -0.34%* 337309478.87 * -0.88%* 338708678.82 * -0.47%*
Hmean unixbench-spawn-1 5571.78 ( 0.00%) 5423.03 ( -2.67%) 5076.02 * -8.90%* 5543.08 ( -0.52%)
Hmean unixbench-spawn-512 63999.96 ( 0.00%) 63485.41 ( -0.80%) 63705.16 ( -0.46%) 67486.34 * 5.45%*
Hmean unixbench-execl-1 3587.15 ( 0.00%) 3624.44 * 1.04%* 3614.43 * 0.76%* 3639.57 * 1.46%*
Hmean unixbench-execl-512 14184.17 ( 0.00%) 13784.17 ( -2.82%) 13985.35 ( -1.40%) 13598.22 ( -4.13%)

~~~~~~~~~~~~~~~~~~
~ DeathStarBench ~
~~~~~~~~~~~~~~~~~~

tl;dr

- Similar trend as hackbench except in NPS4 mode with 8CCXs (one
socket), SIS_NODE_LIMIT and SIS_NODE_TOPOEXT are noticeably
worse than SIS_NODE but all are bad.

o NPS1

CCD Scaling tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1 1 0% 0.30% 0.34% 0.79%
2 2 0% 0.17% 0.78% 0.91%
4 4 0% -0.40% 0.91% 1.61%
8 8 0% -7.95% -6.73% -1.56%

o NPS2

CCD Scaling tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1 1 0% 0.34% 0.07% -0.62%
2 2 0% -0.02% 0.24% -1.15%
4 4 0% -12.34% -6.47% -7.80% * High Run to Run Variance (~10%)
8 8 0% -12.41% -12.83% -9.85%

o NPS4

CCD Scaling tip SIS_NODE SIS_NODE_LIMIT SIS_NODE_TOPOEXT
1 1 0% -1.32% -1.25% -1.09%
2 2 0% -1.53% -1.62% -1.73%
4 4 0% 7.19% 9.08% 5.75%
8 8 0% -4.66% -9.68% -7.52%

--

Conclusion seems to be that most workloads would like to run on an idle
thread as quickly as possible, however, once the system becomes
overloaded, even iterating over the groups to find an idle CPU outside
of the target group can affect the workload performance. TOPOEXT is a
clean way to limit search (as long as marking the boundaries can be
done in a clean way) but there are concerns about the load balancing
jitters the new domain will introduce. There will also be an increase
in amount of C2C transfers as some of the shared data structures are
accessed and modified (for example sched_domain_shared->has_idle_cores
updates).

I'll go get some additional data for some of the data points mentioned
above. Meanwhile if you would like any additional data, please do let
me know. I'll also try to see if a dynamic limit for SIS_NODE_LIMIT
based on Chenyu's SIS_UTIL / ILB_UTIL [3] logic helps.

[3] https://lore.kernel.org/all/bc96b53efb712337a645e2c2a340975545ed5a28.1686554037.git.yu.c.chen@intel.com/

--
Thanks and Regards,
Prateek