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SubjectRe: [PATCH v6 0/4] sched/fair: Improve scan efficiency of SIS
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Hello Abel,

I've retested the patches with on the updated tip and the results
are still promising.

tl;dr

o Hackbench sees improvements when the machine is overloaded.
o tbench shows improvements when the machine is overloaded.
o The unixbench regression seen previously seems to be unrelated
to the patch as the spawn test scores are vastly different
after a reboot/kexec for the same kernel.
o Other benchmarks show slight improvements or are comparable to
the numbers on tip.

Following are the results from running standard benchmarks on a
dual socket Zen3 (2 x 64C/128T) machine configured in different
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

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

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

Following are the Kernel versions:

tip: 6.2.0-rc2 tip:sched/core at
commit: bbd0b031509b "sched/rseq: Fix concurrency ID handling of usermodehelper kthreads"
sis_short: tip + series

The patch applied cleanly on the tip.

Benchmark Results:

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

NPS1

Test: tip sis_core
1-groups: 4.36 (0.00 pct) 4.17 (4.35 pct)
2-groups: 5.17 (0.00 pct) 5.03 (2.70 pct)
4-groups: 4.17 (0.00 pct) 4.14 (0.71 pct)
8-groups: 4.64 (0.00 pct) 4.63 (0.21 pct)
16-groups: 5.43 (0.00 pct) 5.32 (2.02 pct)

NPS2

Test: tip sis_core
1-groups: 4.43 (0.00 pct) 4.27 (3.61 pct)
2-groups: 4.61 (0.00 pct) 4.92 (-6.72 pct) *
2-groups: 4.52 (0.00 pct) 4.55 (-0.66 pct) [Verification Run]
4-groups: 4.25 (0.00 pct) 4.10 (3.52 pct)
8-groups: 4.91 (0.00 pct) 4.53 (7.73 pct)
16-groups: 5.84 (0.00 pct) 5.54 (5.13 pct)

NPS4

Test: tip sis_core
1-groups: 4.34 (0.00 pct) 4.23 (2.53 pct)
2-groups: 4.64 (0.00 pct) 4.84 (-4.31 pct)
4-groups: 4.20 (0.00 pct) 4.17 (0.71 pct)
8-groups: 5.21 (0.00 pct) 5.06 (2.87 pct)
16-groups: 6.24 (0.00 pct) 5.60 (10.25 pct)

~~~~~~~~~~~~
~ schbench ~
~~~~~~~~~~~~

NPS1

#workers: tip sis_core
1: 36.00 (0.00 pct) 23.00 (36.11 pct)
2: 37.00 (0.00 pct) 37.00 (0.00 pct)
4: 37.00 (0.00 pct) 38.00 (-2.70 pct)
8: 47.00 (0.00 pct) 52.00 (-10.63 pct)
16: 64.00 (0.00 pct) 65.00 (-1.56 pct)
32: 109.00 (0.00 pct) 111.00 (-1.83 pct)
64: 222.00 (0.00 pct) 215.00 (3.15 pct)
128: 515.00 (0.00 pct) 486.00 (5.63 pct)
256: 39744.00 (0.00 pct) 47808.00 (-20.28 pct) * (Machine Overloaded ~ 2 tasks per rq)
256: 43242.00 (0.00 pct) 42293.00 (2.19 pct) [Verification Run]
512: 81280.00 (0.00 pct) 76416.00 (5.98 pct)

NPS2

#workers: tip sis_core
1: 27.00 (0.00 pct) 27.00 (0.00 pct)
2: 31.00 (0.00 pct) 30.00 (3.22 pct)
4: 38.00 (0.00 pct) 37.00 (2.63 pct)
8: 50.00 (0.00 pct) 46.00 (8.00 pct)
16: 66.00 (0.00 pct) 68.00 (-3.03 pct)
32: 116.00 (0.00 pct) 113.00 (2.58 pct)
64: 210.00 (0.00 pct) 228.00 (-8.57 pct) *
64: 206.00 (0.00 pct) 219.00 (-6.31 pct) [Verification Run]
128: 523.00 (0.00 pct) 559.00 (-6.88 pct) *
128: 474.00 (0.00 pct) 497.00 (-4.85 pct) [Verification Run]
256: 44864.00 (0.00 pct) 47040.00 (-4.85 pct)
512: 78464.00 (0.00 pct) 81280.00 (-3.58 pct)

NPS4

#workers: tip sis_core
1: 32.00 (0.00 pct) 27.00 (15.62 pct)
2: 32.00 (0.00 pct) 35.00 (-9.37 pct)
4: 34.00 (0.00 pct) 41.00 (-20.58 pct)
8: 58.00 (0.00 pct) 58.00 (0.00 pct)
16: 67.00 (0.00 pct) 69.00 (-2.98 pct)
32: 118.00 (0.00 pct) 112.00 (5.08 pct)
64: 224.00 (0.00 pct) 209.00 (6.69 pct)
128: 533.00 (0.00 pct) 519.00 (2.62 pct)
256: 43456.00 (0.00 pct) 45248.00 (-4.12 pct)
512: 78976.00 (0.00 pct) 76160.00 (3.56 pct)


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

NPS1

Clients: tip sis_core
1 539.96 (0.00 pct) 538.19 (-0.32 pct)
2 1068.21 (0.00 pct) 1063.04 (-0.48 pct)
4 1994.76 (0.00 pct) 1990.47 (-0.21 pct)
8 3602.30 (0.00 pct) 3496.07 (-2.94 pct)
16 6075.49 (0.00 pct) 6061.74 (-0.22 pct)
32 11641.07 (0.00 pct) 11904.58 (2.26 pct)
64 21529.16 (0.00 pct) 22124.81 (2.76 pct)
128 30852.92 (0.00 pct) 31258.56 (1.31 pct)
256 51901.20 (0.00 pct) 53249.69 (2.59 pct)
512 46797.40 (0.00 pct) 54477.79 (16.41 pct)
1024 46057.28 (0.00 pct) 53676.58 (16.54 pct)

NPS2

Clients: tip sis_core
1 536.11 (0.00 pct) 541.18 (0.94 pct)
2 1044.58 (0.00 pct) 1064.16 (1.87 pct)
4 2043.92 (0.00 pct) 2017.84 (-1.27 pct)
8 3572.50 (0.00 pct) 3494.83 (-2.17 pct)
16 6040.97 (0.00 pct) 5530.10 (-8.45 pct) *
16 5814.03 (0.00 pct) 6012.33 (-8.45 pct) [Verification Run]
32 10794.10 (0.00 pct) 10841.68 (0.44 pct)
64 20905.89 (0.00 pct) 21438.82 (2.54 pct)
128 30885.39 (0.00 pct) 30064.78 (-2.65 pct)
256 48901.25 (0.00 pct) 51395.08 (5.09 pct)
512 49673.91 (0.00 pct) 51725.89 (4.13 pct)
1024 47626.34 (0.00 pct) 52662.01 (10.57 pct)

NPS4

Clients: tip sis_core
1 544.91 (0.00 pct) 544.66 (-0.04 pct)
2 1046.49 (0.00 pct) 1072.42 (2.47 pct)
4 2007.11 (0.00 pct) 1970.05 (-1.84 pct)
8 3590.66 (0.00 pct) 3670.45 (2.22 pct)
16 5956.60 (0.00 pct) 6045.07 (1.48 pct)
32 10431.73 (0.00 pct) 10439.40 (0.07 pct)
64 21563.37 (0.00 pct) 19344.05 (-10.29 pct) *
64 19387.71 (0.00 pct) 19050.47 (-1.73 pct) [Verification Run]
128 30352.16 (0.00 pct) 26998.85 (-11.04 pct) *
128 29110.99 (0.00 pct) 29690.37 (1.99 pct) [Verification Run]
256 49504.51 (0.00 pct) 50921.66 (2.86 pct)
512 44916.61 (0.00 pct) 52176.11 (16.16 pct)
1024 49986.21 (0.00 pct) 51639.91 (3.30 pct)


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

NPS1

10 Runs:

Test: tip sis_core
Copy: 339390.30 (0.00 pct) 324656.88 (-4.34 pct)
Scale: 212472.78 (0.00 pct) 210641.39 (-0.86 pct)
Add: 247598.48 (0.00 pct) 241669.10 (-2.39 pct)
Triad: 261852.07 (0.00 pct) 252088.55 (-3.72 pct)

100 Runs:

Test: tip sis_core
Copy: 335938.02 (0.00 pct) 331491.32 (-1.32 pct)
Scale: 212597.92 (0.00 pct) 218705.84 (2.87 pct)
Add: 248294.62 (0.00 pct) 243830.42 (-1.79 pct)
Triad: 258400.88 (0.00 pct) 248178.42 (-3.95 pct)

NPS2

10 Runs:

Test: tip sis_core
Copy: 334500.32 (0.00 pct) 335317.70 (0.24 pct)
Scale: 216804.76 (0.00 pct) 217862.71 (0.48 pct)
Add: 250787.33 (0.00 pct) 258839.00 (3.21 pct)
Triad: 259451.40 (0.00 pct) 264847.88 (2.07 pct)

100 Runs:

Test: tip sis_core
Copy: 326385.13 (0.00 pct) 338030.70 (3.56 pct)
Scale: 216440.37 (0.00 pct) 230053.24 (6.28 pct)
Add: 255062.22 (0.00 pct) 259197.23 (1.62 pct)
Triad: 265442.03 (0.00 pct) 271365.65 (2.23 pct)

NPS4

10 Runs:

Test: tip sis_core
Copy: 363927.86 (0.00 pct) 361014.15 (-0.80 pct)
Scale: 238190.49 (0.00 pct) 242176.02 (1.67 pct)
Add: 262806.49 (0.00 pct) 266348.50 (1.34 pct)
Triad: 276492.33 (0.00 pct) 276769.10 (0.10 pct)

100 Runs:

Test: tip sis_core
Copy: 365041.37 (0.00 pct) 349299.35 (-4.31 pct)
Scale: 239295.27 (0.00 pct) 229944.85 (-3.90 pct)
Add: 264085.21 (0.00 pct) 252651.56 (-4.32 pct)
Triad: 279664.56 (0.00 pct) 274254.22 (-1.93 pct)

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

o NPS1

tip: 131328.67 (var: 2.97%)
sis_core: 131702.33 (var: 3.61%) (0.28%)

o NPS2:

tip: 132482.33 (var: 2.06%)
sis_core: 132338.33 (var: 0.97%) (-0.11%)

o NPS4:

tip: 134130.00 (var: 4.12%)
sis_core: 133224.33 (var: 4.13%) (-0.67%)

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

o NPS1

Test Metric Parallelism tip sis_core
unixbench-dhry2reg Hmean unixbench-dhry2reg-1 48770555.20 ( 0.00%) 49025161.73 ( 0.52%)
unixbench-dhry2reg Hmean unixbench-dhry2reg-512 6268185467.60 ( 0.00%) 6266351964.20 ( -0.03%)
unixbench-syscall Amean unixbench-syscall-1 2685321.17 ( 0.00%) 2694468.30 * -0.34%*
unixbench-syscall Amean unixbench-syscall-512 7291476.20 ( 0.00%) 7295087.67 ( -0.05%)
unixbench-pipe Hmean unixbench-pipe-1 2480858.53 ( 0.00%) 2536923.44 * 2.26%*
unixbench-pipe Hmean unixbench-pipe-512 300739256.62 ( 0.00%) 303470605.93 * 0.91%*
unixbench-spawn Hmean unixbench-spawn-1 4358.14 ( 0.00%) 4104.88 ( -5.81%) * (Known to be unstable)
unixbench-spawn Hmean unixbench-spawn-1 4711.00 ( 0.00%) 4006.20 ( -14.96%) [Verification Run]
unixbench-spawn Hmean unixbench-spawn-512 76497.32 ( 0.00%) 75555.94 * -1.23%*
unixbench-execl Hmean unixbench-execl-1 4147.12 ( 0.00%) 4157.33 ( 0.25%)
unixbench-execl Hmean unixbench-execl-512 12435.26 ( 0.00%) 11992.43 ( -3.56%)

o NPS2

Test Metric Parallelism tip sis_core
unixbench-dhry2reg Hmean unixbench-dhry2reg-1 48872335.50 ( 0.00%) 48902553.70 ( 0.06%)
unixbench-dhry2reg Hmean unixbench-dhry2reg-512 6264134378.20 ( 0.00%) 6260631689.40 ( -0.06%)
unixbench-syscall Amean unixbench-syscall-1 2683903.13 ( 0.00%) 2694829.17 * -0.41%*
unixbench-syscall Amean unixbench-syscall-512 7746773.60 ( 0.00%) 7493782.67 * 3.27%*
unixbench-pipe Hmean unixbench-pipe-1 2476724.23 ( 0.00%) 2537127.96 * 2.44%*
unixbench-pipe Hmean unixbench-pipe-512 300277350.41 ( 0.00%) 302979776.19 * 0.90%*
unixbench-spawn Hmean unixbench-spawn-1 5026.50 ( 0.00%) 4680.63 ( -6.88%) *
unixbench-spawn Hmean unixbench-spawn-1 5421.70 ( 0.00%) 5311.50 ( -2.03%) [Verification Run]
unixbench-spawn Hmean unixbench-spawn-512 80549.70 ( 0.00%) 78888.60 ( -2.06%)
unixbench-execl Hmean unixbench-execl-1 4151.70 ( 0.00%) 3913.76 * -5.73%* *
unixbench-execl Hmean unixbench-execl-1 4304.30 ( 0.00%) 4303.20 ( -0.02%) [Verification run]
unixbench-execl Hmean unixbench-execl-512 13605.15 ( 0.00%) 13129.23 ( -3.50%)

o NPS4

Test Metric Parallelism tip sis_core
unixbench-dhry2reg Hmean unixbench-dhry2reg-1 48506771.20 ( 0.00%) 48894866.70 ( 0.80%)
unixbench-dhry2reg Hmean unixbench-dhry2reg-512 6280954362.50 ( 0.00%) 6282759876.40 ( 0.03%)
unixbench-syscall Amean unixbench-syscall-1 2687259.30 ( 0.00%) 2695379.93 * -0.30%*
unixbench-syscall Amean unixbench-syscall-512 7350275.67 ( 0.00%) 7366923.73 ( -0.23%)
unixbench-pipe Hmean unixbench-pipe-1 2478893.01 ( 0.00%) 2540015.88 * 2.47%*
unixbench-pipe Hmean unixbench-pipe-512 301830155.61 ( 0.00%) 304305539.27 * 0.82%*
unixbench-spawn Hmean unixbench-spawn-1 5208.55 ( 0.00%) 5273.11 ( 1.24%)
unixbench-spawn Hmean unixbench-spawn-512 80745.79 ( 0.00%) 81940.71 * 1.48%*
unixbench-execl Hmean unixbench-execl-1 4072.72 ( 0.00%) 4126.13 * 1.31%*
unixbench-execl Hmean unixbench-execl-512 13746.56 ( 0.00%) 12848.77 ( -6.53%) *
unixbench-execl Hmean unixbench-execl-512 13898.30 ( 0.00%) 13959.70 ( 0.44%) [Verification Run]

On 10/19/2022 5:58 PM, Abel Wu wrote:
> This patchset tries to improve SIS scan efficiency by recording idle
> cpus in a cpumask for each LLC which will be used as a target cpuset
> in the domain scan. The cpus are recorded at CORE granule to avoid
> tasks being stack on same core.
>
> v5 -> v6:
> - Rename SIS_FILTER to SIS_CORE as it can only be activated when
> SMT is enabled and better describes the behavior of CORE granule
> update & load delivery.
> - Removed the part of limited scan for idle cores since it might be
> better to open another thread to discuss the strategies such as
> limited or scaled depth. But keep the part of full scan for idle
> cores when LLC is overloaded because SIS_CORE can greatly reduce
> the overhead of full scan in such case.
> - Removed the state of sd_is_busy which indicates an LLC is fully
> busy and we can safely skip the SIS domain scan. I would prefer
> leave this to SIS_UTIL.
> - The filter generation mechanism is replaced by in-place updates
> during domain scan to better deal with partial scan failures.
> - Collect Reviewed-bys from Tim Chen
>
> v4 -> v5:
> - Add limited scan for idle cores when overloaded, suggested by Mel
> - Split out several patches since they are irrelevant to this scope
> - Add quick check on ttwu_pending before core update
> - Wrap the filter into SIS_FILTER feature, suggested by Chen Yu
> - Move the main filter logic to the idle path, because the newidle
> balance can bail out early if rq->avg_idle is small enough and
> lose chances to update the filter.
>
> v3 -> v4:
> - Update filter in load_balance rather than in the tick
> - Now the filter contains unoccupied cpus rather than overloaded ones
> - Added mechanisms to deal with the false positive cases
>
> v2 -> v3:
> - Removed sched-idle balance feature and focus on SIS
> - Take non-CFS tasks into consideration
> - Several fixes/improvement suggested by Josh Don
>
> v1 -> v2:
> - Several optimizations on sched-idle balancing
> - Ignore asym topos in can_migrate_task
> - Add more benchmarks including SIS efficiency
> - Re-organize patch as suggested by Mel Gorman
>
> Abel Wu (4):
> sched/fair: Skip core update if task pending
> sched/fair: Ignore SIS_UTIL when has_idle_core
> sched/fair: Introduce SIS_CORE
> sched/fair: Deal with SIS scan failures
>
> include/linux/sched/topology.h | 15 ++++
> kernel/sched/fair.c | 122 +++++++++++++++++++++++++++++----
> kernel/sched/features.h | 7 ++
> kernel/sched/sched.h | 3 +
> kernel/sched/topology.c | 8 ++-
> 5 files changed, 141 insertions(+), 14 deletions(-)
>

Testing with couple of larger workloads like SpecJBB are still underway.
I'll update the thread with the results once they are done. The idea
is promising. I'll also try to run schbench / hackbench pinned in a
manner such that all wakeups happen on an external LLC to spot any
impact of rapid changes to the idle cpu mask of an external LLC.
Please let me know if you would like me to test or get data for any
particular benchmark from my test setup.

--
Thanks and Regards,
Prateek

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