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SubjectRe: [PATCH v5 0/7] Add latency priority for CFS class
Hi Prateek,

Thanks for testing the patchset on AMD and the test report below.

On Wed, 12 Oct 2022 at 16:54, K Prateek Nayak <kprateek.nayak@amd.com> wrote:
>
> Hello Vincent,
>
> Sharing results from testing on dual socket Zen3 system (2 x 64C/128T)
>
> tl;dr
>
> o I don't see any regression when workloads are running with
> DEFAULT_LATENCY_NICE
> o I can reproduce similar results as one reported in Patch 4 for
> hackbench with latency nice 19 and hackbench and cyclictest
> with various combination of latency nice values.
> o I can see improvements to tail latency for schbench with hackbench
> running in the background.
> o There is an unexpected non-linear behavior observed for couple of
> cases that I cannot explain yet. (Marked with "^" in detailed results)
> I have not yet gotten to the bottom of it but if I've missed
> something, please do let me know.
>
> Detailed results are shared below:
>
> On 9/25/2022 8:09 PM, Vincent Guittot wrote:
> > This patchset restarts the work about adding a latency priority to describe
> > the latency tolerance of cfs tasks.
> >
> > The patches [1-3] have been done by Parth:
> > https://lore.kernel.org/lkml/20200228090755.22829-1-parth@linux.ibm.com/
> >
> > I have just rebased and moved the set of latency priority outside the
> > priority update. I have removed the reviewed tag because the patches
> > are 2 years old.
> >
> > This aims to be a generic interface and the following patches is one use
> > of it to improve the scheduling latency of cfs tasks.
> >
> > The patch [4] uses latency nice priority to define a latency offset
> > and then decide if a cfs task can or should preempt the current
> > running task. The patch gives some tests results with cyclictests and
> > hackbench to highlight the benefit of latency priority for short
> > interactive task or long intensive tasks.
> >
> > Patch [5] adds the support of latency nice priority to task group by
> > adding a cpu.latency.nice field. The range is [-20:19] as for setting task
> > latency priority.
> >
> > Patch [6] makes sched_core taking into account the latency offset.
> >
> > Patch [7] adds a rb tree to cover some corner cases where the latency
> > sensitive task (priority < 0) is preempted by high priority task (RT/DL)
> > or fails to preempt them. This patch ensures that tasks will have at least
> > a slice of sched_min_granularity in priority at wakeup. The patch gives
> > results to show the benefit in addition to patch 4.
> >
> > I have also backported the patchset on a dragonboard RB3 with an android
> > mainline kernel based on v5.18 for a quick test. I have used the
> > TouchLatency app which is part of AOSP and described to be a very good
> > test to highlight jitter and jank frame sources of a system [1].
> > In addition to the app, I have added some short running tasks waking-up
> > regularly (to use the 8 cpus for 4 ms every 37777us) to stress the system
> > without overloading it (and disabling EAS). The 1st results shows that the
> > patchset helps to reduce the missed deadline frames from 5% to less than
> > 0.1% when the cpu.latency.nice of task group are set.
> >
> > I have also tested the patchset with the modified version of the alsa
> > latency test that has been shared by Tim. The test quickly xruns with
> > default latency nice priority 0 but is able to run without underuns with
> > a latency -20 and hackbench running simultaneously.
> >
> >
> > [1] https://source.android.com/docs/core/debug/eval_perf#touchlatency
>
> 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
>
> Benchmark Results:
>
> Kernel versions:
> - tip: 5.19.0 tip sched/core
> - latency_nice: 5.19.0 tip sched/core + this series
>
> When we started testing, the tip was at:
> commit 7e9518baed4c ("sched/fair: Move call to list_last_entry() in detach_tasks")
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~ hackbench - DEFAULT_LATENCY_NICE ~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> NPS1
>
> Test: tip latency_nice
> 1-groups: 4.23 (0.00 pct) 4.06 (4.01 pct)
> 2-groups: 4.93 (0.00 pct) 4.89 (0.81 pct)
> 4-groups: 5.32 (0.00 pct) 5.31 (0.18 pct)
> 8-groups: 5.46 (0.00 pct) 5.54 (-1.46 pct)
> 16-groups: 7.31 (0.00 pct) 7.33 (-0.27 pct)
>
> NPS2
>
> Test: tip latency_nice
> 1-groups: 4.19 (0.00 pct) 4.12 (1.67 pct)
> 2-groups: 4.77 (0.00 pct) 4.82 (-1.04 pct)
> 4-groups: 5.15 (0.00 pct) 5.17 (-0.38 pct)
> 8-groups: 5.47 (0.00 pct) 5.48 (-0.18 pct)
> 16-groups: 6.63 (0.00 pct) 6.65 (-0.30 pct)
>
> NPS4
>
> Test: tip latency_nice
> 1-groups: 4.23 (0.00 pct) 4.31 (-1.89 pct)
> 2-groups: 4.78 (0.00 pct) 4.75 (0.62 pct)
> 4-groups: 5.17 (0.00 pct) 5.24 (-1.35 pct)
> 8-groups: 5.63 (0.00 pct) 5.59 (0.71 pct)
> 16-groups: 7.88 (0.00 pct) 7.09 (10.02 pct)
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~ schbench - DEFAULT_LATENCY_NICE ~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> NPS1
>
> #workers: tip latency_nice
> 1: 22.00 (0.00 pct) 21.00 (4.54 pct)
> 2: 34.00 (0.00 pct) 34.00 (0.00 pct)
> 4: 37.00 (0.00 pct) 40.00 (-8.10 pct)
> 8: 55.00 (0.00 pct) 49.00 (10.90 pct)
> 16: 69.00 (0.00 pct) 66.00 (4.34 pct)
> 32: 113.00 (0.00 pct) 117.00 (-3.53 pct)
> 64: 219.00 (0.00 pct) 242.00 (-10.50 pct) *
> 64: 219.00 (0.00 pct) 194.00 (11.41 pct) [Verification Run]
> 128: 506.00 (0.00 pct) 513.00 (-1.38 pct)
> 256: 45440.00 (0.00 pct) 44992.00 (0.98 pct)
> 512: 76672.00 (0.00 pct) 83328.00 (-8.68 pct)
>
> NPS2
>
> #workers: tip latency_nice
> 1: 31.00 (0.00 pct) 20.00 (35.48 pct)
> 2: 36.00 (0.00 pct) 28.00 (22.22 pct)
> 4: 45.00 (0.00 pct) 37.00 (17.77 pct)
> 8: 47.00 (0.00 pct) 51.00 (-8.51 pct)
> 16: 66.00 (0.00 pct) 69.00 (-4.54 pct)
> 32: 114.00 (0.00 pct) 113.00 (0.87 pct)
> 64: 215.00 (0.00 pct) 215.00 (0.00 pct)
> 128: 495.00 (0.00 pct) 529.00 (-6.86 pct) *
> 128: 495.00 (0.00 pct) 416.00 (15.95 pct) [Verification Run]
> 256: 48576.00 (0.00 pct) 46912.00 (3.42 pct)
> 512: 79232.00 (0.00 pct) 82560.00 (-4.20 pct)
>
> NPS4
>
> #workers: tip latency_nice
> 1: 30.00 (0.00 pct) 34.00 (-13.33 pct)
> 2: 34.00 (0.00 pct) 42.00 (-23.52 pct)
> 4: 41.00 (0.00 pct) 42.00 (-2.43 pct)
> 8: 60.00 (0.00 pct) 55.00 (8.33 pct)
> 16: 68.00 (0.00 pct) 69.00 (-1.47 pct)
> 32: 116.00 (0.00 pct) 115.00 (0.86 pct)
> 64: 224.00 (0.00 pct) 223.00 (0.44 pct)
> 128: 495.00 (0.00 pct) 677.00 (-36.76 pct) *
> 128: 495.00 (0.00 pct) 388.00 (21.61 pct) [Verification Run]
> 256: 45888.00 (0.00 pct) 44608.00 (2.78 pct)
> 512: 78464.00 (0.00 pct) 81536.00 (-3.91 pct)
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~ tbench - DEFAULT_LATENCY_NICE ~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> NPS1
>
> Clients: tip latency_nice
> 1 550.66 (0.00 pct) 546.63 (-0.73 pct)
> 2 1009.69 (0.00 pct) 1016.40 (0.66 pct)
> 4 1795.32 (0.00 pct) 1773.95 (-1.19 pct)
> 8 2971.16 (0.00 pct) 2930.26 (-1.37 pct)
> 16 4627.98 (0.00 pct) 4727.82 (2.15 pct)
> 32 8065.15 (0.00 pct) 9019.11 (11.82 pct)
> 64 14994.32 (0.00 pct) 15100.22 (0.70 pct)
> 128 5175.73 (0.00 pct) 18223.69 (252.09 pct) *
> 128 20029.53 (0.00 pct) 20517.17 (2.43 pct) [Verification Run]
> 256 48763.57 (0.00 pct) 44463.63 (-8.81 pct)
> 512 43780.78 (0.00 pct) 44170.21 (0.88 pct)
> 1024 40341.84 (0.00 pct) 40883.10 (1.34 pct)
>
> NPS2
>
> Clients: tip latency_nice
> 1 551.06 (0.00 pct) 547.43 (-0.65 pct)
> 2 1000.76 (0.00 pct) 1014.83 (1.40 pct)
> 4 1737.02 (0.00 pct) 1742.30 (0.30 pct)
> 8 2992.31 (0.00 pct) 2951.59 (-1.36 pct)
> 16 4579.29 (0.00 pct) 4558.05 (-0.46 pct)
> 32 9120.73 (0.00 pct) 8122.06 (-10.94 pct) *
> 32 8814.62 (0.00 pct) 8965.54 (1.71 pct) [Verification Run]
> 64 14918.58 (0.00 pct) 14890.93 (-0.18 pct)
> 128 20830.61 (0.00 pct) 20410.48 (-2.01 pct)
> 256 47708.18 (0.00 pct) 45312.84 (-5.02 pct) *
> 256 44941.88 (0.00 pct) 44555.92 (-0.85 pct) [Verification Run]
> 512 43721.79 (0.00 pct) 43653.43 (-0.15 pct)
> 1024 40920.49 (0.00 pct) 41162.17 (0.59 pct)
>
> NPS4
>
> Clients: tip latency_nice
> 1 549.22 (0.00 pct) 539.81 (-1.71 pct)
> 2 1000.08 (0.00 pct) 1010.12 (1.00 pct)
> 4 1794.78 (0.00 pct) 1736.06 (-3.27 pct)
> 8 3008.50 (0.00 pct) 2952.68 (-1.85 pct)
> 16 4804.71 (0.00 pct) 4454.17 (-7.29 pct) *
> 16 4391.10 (0.00 pct) 4497.43 (2.42 pct) [Verification Run]
> 32 9156.57 (0.00 pct) 8820.05 (-3.67 pct)
> 64 14901.45 (0.00 pct) 14786.25 (-0.77 pct)
> 128 20771.20 (0.00 pct) 19955.11 (-3.92 pct)
> 256 47033.88 (0.00 pct) 44937.51 (-4.45 pct)
> 512 43429.01 (0.00 pct) 42638.81 (-1.81 pct)
> 1024 39271.27 (0.00 pct) 40044.17 (1.96 pct)
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~ stream - DEFAULT_LATENCY_NICE ~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> NPS1
>
> 10 Runs:
>
> Test: tip latency_nice
> Copy: 336311.52 (0.00 pct) 326015.98 (-3.06 pct)
> Scale: 212955.82 (0.00 pct) 208667.27 (-2.01 pct)
> Add: 251518.23 (0.00 pct) 237286.20 (-5.65 pct)
> Triad: 262077.88 (0.00 pct) 258949.80 (-1.19 pct)
>
> 100 Runs:
>
> Test: tip latency_nice
> Copy: 339533.83 (0.00 pct) 335126.73 (-1.29 pct)
> Scale: 194736.72 (0.00 pct) 221151.24 (13.56 pct)
> Add: 218294.54 (0.00 pct) 251427.43 (15.17 pct)
> Triad: 262371.40 (0.00 pct) 260100.85 (-0.86 pct)
>
> NPS2
>
> 10 Runs:
>
> Test: tip latency_nice
> Copy: 335277.15 (0.00 pct) 339614.38 (1.29 pct)
> Scale: 220990.24 (0.00 pct) 221052.78 (0.02 pct)
> Add: 264156.13 (0.00 pct) 263684.19 (-0.17 pct)
> Triad: 268707.53 (0.00 pct) 272610.96 (1.45 pct)
>
> 100 Runs:
>
> Test: tip latency_nice
> Copy: 334913.73 (0.00 pct) 339001.88 (1.22 pct)
> Scale: 230522.47 (0.00 pct) 229848.86 (-0.29 pct)
> Add: 264567.28 (0.00 pct) 264288.34 (-0.10 pct)
> Triad: 272974.23 (0.00 pct) 272045.17 (-0.34 pct)
>
> NPS4
>
> 10 Runs:
>
> Test: tip latency_nice
> Copy: 299432.31 (0.00 pct) 307649.18 (2.74 pct)
> Scale: 217998.17 (0.00 pct) 205763.70 (-5.61 pct)
> Add: 234305.46 (0.00 pct) 226381.75 (-3.38 pct)
> Triad: 244369.15 (0.00 pct) 254225.30 (4.03 pct)
>
> 100 Runs:
>
> Test: tip latency_nice
> Copy: 344421.25 (0.00 pct) 322189.81 (-6.45 pct)
> Scale: 237998.44 (0.00 pct) 227709.58 (-4.32 pct)
> Add: 257501.82 (0.00 pct) 244009.58 (-5.23 pct)
> Triad: 267686.50 (0.00 pct) 251840.25 (-5.91 pct)
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~ Test cases for Latency Nice ~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Note: Latency Nice might be referred to as LN in the data below. Latency Nice
> value was set using a wrapper script for all the workload threads during the
> testing.
> All the test results reported below are for NPS1 configuration.
>
> o Hackbench Pipes (100000 loops, threads)
>
> Test: tip Latency Nice: -20 Latency Nice: 0 Latency Nice: 19
> 1-groups: 4.23 (0.00 pct) 4.39 (-3.78 pct) 3.99 (5.67 pct) 3.88 (8.27 pct)
> 2-groups: 4.93 (0.00 pct) 4.91 (0.40 pct) 4.69 (4.86 pct) 4.59 (6.89 pct)
> 4-groups: 5.32 (0.00 pct) 5.37 (-0.93 pct) 5.19 (2.44 pct) 5.05 (5.07 pct)
> 8-groups: 5.46 (0.00 pct) 5.90 (-8.05 pct) 5.34 (2.19 pct) 5.17 (5.31 pct)
> 16-groups: 7.31 (0.00 pct) 7.99 (-9.30 pct) 6.96 (4.78 pct) 6.51 (10.94 pct)
>
> o Only Hackbench with different Latency Nice Values
>
> > Loops: 100000
>
> - Pipe (Process)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 3.77 (0.00 pct) 4.23 (-12.20 pct) 3.83 (-1.59 pct)
> 2-groups: 4.39 (0.00 pct) 4.73 (-7.74 pct) 4.31 (1.82 pct)
> 4-groups: 4.80 (0.00 pct) 5.07 (-5.62 pct) 4.68 (2.50 pct)
> 8-groups: 4.95 (0.00 pct) 5.68 (-14.74 pct) 4.76 (3.83 pct)
> 16-groups: 6.47 (0.00 pct) 7.87 (-21.63 pct) 6.08 (6.02 pct)
>
> - Socket (Thread)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 6.08 (0.00 pct) 5.99 (1.48 pct) 6.08 (0.00 pct)
> 2-groups: 6.15 (0.00 pct) 6.25 (-1.62 pct) 6.14 (0.16 pct)
> 4-groups: 6.39 (0.00 pct) 6.42 (-0.46 pct) 6.44 (-0.78 pct)
> 8-groups: 8.51 (0.00 pct) 9.01 (-5.87 pct) 8.36 (1.76 pct)
> 16-groups: 12.48 (0.00 pct) 15.32 (-22.75 pct) 12.72 (-1.92 pct)
>
> - Socket (Process)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 6.44 (0.00 pct) 5.50 (14.59 pct) ^ 6.43 (0.15 pct)
> 2-groups: 6.55 (0.00 pct) 5.56 (15.11 pct) ^ 6.36 (2.90 pct)
> 4-groups: 6.74 (0.00 pct) 6.19 (8.16 pct) ^ 6.69 (0.74 pct)
> 8-groups: 8.03 (0.00 pct) 8.29 (-3.23 pct) 8.02 (0.12 pct)
> 16-groups: 12.25 (0.00 pct) 14.11 (-15.18 pct) 12.41 (-1.30 pct)

I don't see any improvement with LN:-20 but only for LN:19

How many iterations do you run ? Could it be that the results vary
between iterations ? For some configuration I have a stddev of 10-20%
for LN:0 and LN:-20

>
> > Loops: 2160 (Same as in testing)
>
> - Pipe (Thread)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 0.10 (0.00 pct) 0.12 (-20.00 pct) 0.10 (0.00 pct)
> 2-groups: 0.12 (0.00 pct) 0.15 (-25.00 pct) 0.11 (8.33 pct)
> 4-groups: 0.14 (0.00 pct) 0.18 (-28.57 pct) 0.15 (-7.14 pct)
> 8-groups: 0.17 (0.00 pct) 0.24 (-41.17 pct) 0.17 (0.00 pct)
> 16-groups: 0.26 (0.00 pct) 0.33 (-26.92 pct) 0.21 (19.23 pct)
>
> - Pipe (Process)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 0.10 (0.00 pct) 0.12 (-20.00 pct) 0.10 (0.00 pct)
> 2-groups: 0.12 (0.00 pct) 0.16 (-33.33 pct) 0.12 (0.00 pct)
> 4-groups: 0.14 (0.00 pct) 0.17 (-21.42 pct) 0.13 (7.14 pct)
> 8-groups: 0.16 (0.00 pct) 0.24 (-50.00 pct) 0.16 (0.00 pct)
> 16-groups: 0.23 (0.00 pct) 0.33 (-43.47 pct) 0.19 (17.39 pct)
>
> - Socket (Thread)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 0.19 (0.00 pct) 0.18 (5.26 pct) 0.18 (5.26 pct)
> 2-groups: 0.21 (0.00 pct) 0.21 (0.00 pct) 0.20 (4.76 pct)
> 4-groups: 0.22 (0.00 pct) 0.25 (-13.63 pct) 0.22 (0.00 pct)
> 8-groups: 0.27 (0.00 pct) 0.36 (-33.33 pct) 0.27 (0.00 pct)
> 16-groups: 0.42 (0.00 pct) 0.55 (-30.95 pct) 0.40 (4.76 pct)
>
> - Socket (Process)
>
> Test: Latency Nice: 0 Latency Nice: -20 Latency Nice: 19
> 1-groups: 0.17 (0.00 pct) 0.17 (0.00 pct) 0.17 (0.00 pct)
> 2-groups: 0.19 (0.00 pct) 0.20 (-5.26 pct) 0.19 (0.00 pct)
> 4-groups: 0.20 (0.00 pct) 0.22 (-10.00 pct) 0.20 (0.00 pct)
> 8-groups: 0.25 (0.00 pct) 0.32 (-28.00 pct) 0.25 (0.00 pct)
> 16-groups: 0.40 (0.00 pct) 0.51 (-27.50 pct) 0.39 (2.50 pct)
>
> o Hackbench and Cyclictest in NPS1 configuration
>
> perf bench sched messaging -p -t -l 100000 -g 16&
> cyclictest --policy other -D 5 -q -n -H 20000
>
> -----------------------------------------------------------------------------------------------------------------
> |Hackbench | Cyclictest LN = 19 | Cyclictest LN = 0 | Cyclictest LN = -20 |
> |LN |--------------------------------|---------------------------------|-----------------------------|
> |v | Min | Avg | Max | Min | Avg | Max | Min | Avg | Max |
> |--------------|--------|---------|-------------|----------|---------|------------|----------|---------|--------|
> |0 | 54.00 | 117.00 | 3021.67 | 53.67 | 65.33 | 133.00 | 53.67 | 65.00 | 201.33 | ^
> |19 | 50.00 | 100.67 | 3099.33 | 41.00 | 64.33 | 1014.33 | 54.00 | 63.67 | 213.33 |
> |-20 | 53.00 | 169.00 | 11661.67 | 53.67 | 217.33 | 14313.67 | 46.00 | 61.33 | 236.00 | ^
> -----------------------------------------------------------------------------------------------------------------

The latency results look good with Cyclictest LN:0 and hackbench LN:0.
133us max latency. This suggests that your system is not overloaded
and cyclictest doesn't really compete with others to run.

>
> o Hackbench and schbench in NPS1 configuration
>
> perf bench sched messaging -p -t -l 1000000 -g 16&
> schebcnh -m 1 -t 64 -s 30s
>
> ------------------------------------------------------------------------------------------------------------
> |Hackbench | schbench LN = 19 | schbench LN = 0 | schbench LN = -20 |
> |LN |----------------------------|--------------------------------|-----------------------------|
> |v | 90th | 95th | 99th | 90th | 95th | 99th | 90th | 95th | 99th |
> |--------------|--------|--------|----------|---------|---------|------------|---------|----------|--------|
> |0 | 4264 | 6744 | 15664 | 17952 | 32672 | 55488 | 15088 | 25312 | 50112 |
> |19 | 288 | 613 | 2332 | 274 | 1015 | 3628 | 374 | 1394 | 4424 |
> |-20 | 35904 | 47680 | 79744 | 87168 | 113536 | 176896 | 13008 | 21216 | 42560 | ^
> ------------------------------------------------------------------------------------------------------------

For the schbench, your test is 30 seconds long which is longer than
the duration of perf bench sched messaging -p -t -l 1000000 -g 16&

The duration of the latter varies depending of latency nice value so
schbench is disturb more time in some cases
>
> o SpecJBB Multi-JVM
>
> ---------------------------------------------
> | Latency Nice | 0 | 19 |
> ---------------------------------------------
> | max-jOPS | 100% | 109.92% |
> | critical-jOPS | 100% | 153.70% |
> ---------------------------------------------
>
> In most cases, latency nice delivers what it promises.
> Some cases marked with "^" have shown anomalies or non-linear behavior
> that is yet to be root caused. If you've seen something similar during
> your testing, I would love to know what could lead to such a behavior.

I haven't seen anything like the results that you tagged with ^. As a
side note, the numbers of groups (g1 g4 g8 g1) that I used with
hackbench, have been chosen according to my 8 cores system. Your
system is much larger and hackbench may not overload it with such a
small number of groups. Maybe you could try with g32 g64 g128 g256 ?



>
> If you would like more details on the benchmarks results reported above
> or if there is any specific workload you would like me to test on the
> Zen3 machine, please do let me know.
>
> >
> > [..snip..]
> >
>
> --
> Thanks and Regards,
> Prateek
> --
> --
> Thanks and Regards,
> Prateek

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