On Thu, 2021-08-05 at 18:42 +0200, Sebastian Andrzej Siewior wrote:
>
> There was throughput regression in RT compared to previous releases
> (without this series). The regression was (based on my testing) only
> visible in hackbench and was addressed by adding adaptiv spinning to
> RT-mutex. With that we almost back to what we had before :)
Numbers on my box say a throughput regression remains (silly fork bomb
scenario.. yawn), which can be recouped by either turning on all
SL[AU]B features or converting the list_lock to a raw lock. They also
seem to be saying that if you turned on PREEMPT_RT because you care
about RT performance first and foremost (gee), you'll do neither of
those, because either will eliminate an RT performance progression.
-Mike
numbers...
box is old i4790 desktop
perf stat -r10 hackbench -s4096 -l500
full warmup, record, repeat twice for elapsed
SLUB+SLUB_DEBUG only
begin previously reported numbers
5.14.0.g79e92006-tip-rt (5.12-rt based as before, 5.13-rt didn't yet exist)
7,984.52 msec task-clock # 7.565 CPUs utilized ( +- 0.66% )
353,566 context-switches # 44.281 K/sec ( +- 2.77% )
37,685 cpu-migrations # 4.720 K/sec ( +- 6.37% )
12,939 page-faults # 1.620 K/sec ( +- 0.67% )
29,901,079,227 cycles # 3.745 GHz ( +- 0.71% )
14,550,797,818 instructions # 0.49 insn per cycle ( +- 0.47% )
3,056,685,643 branches # 382.826 M/sec ( +- 0.51% )
9,598,083 branch-misses # 0.31% of all branches ( +- 2.11% )
1.05542 +- 0.00409 seconds time elapsed ( +- 0.39% )
1.05990 +- 0.00244 seconds time elapsed ( +- 0.23% ) (repeat)
1.05367 +- 0.00303 seconds time elapsed ( +- 0.29% ) (repeat)
5.14.0.g79e92006-tip-rt +slub-local-lock-v2r3 -0034-mm-slub-convert-kmem_cpu_slab-protection-to-local_lock.patch
6,899.35 msec task-clock # 5.637 CPUs utilized ( +- 0.53% )
420,304 context-switches # 60.919 K/sec ( +- 2.83% )
187,130 cpu-migrations # 27.123 K/sec ( +- 1.81% )
13,206 page-faults # 1.914 K/sec ( +- 0.96% )
25,110,362,933 cycles # 3.640 GHz ( +- 0.49% )
15,853,643,635 instructions # 0.63 insn per cycle ( +- 0.64% )
3,366,261,524 branches # 487.910 M/sec ( +- 0.70% )
14,839,618 branch-misses # 0.44% of all branches ( +- 2.01% )
1.22390 +- 0.00744 seconds time elapsed ( +- 0.61% )
1.21813 +- 0.00907 seconds time elapsed ( +- 0.74% ) (repeat)
1.22097 +- 0.00952 seconds time elapsed ( +- 0.78% ) (repeat)
repeat of above with raw list_lock
8,072.62 msec task-clock # 7.605 CPUs utilized ( +- 0.49% )
359,514 context-switches # 44.535 K/sec ( +- 4.95% )
35,285 cpu-migrations # 4.371 K/sec ( +- 5.82% )
13,503 page-faults # 1.673 K/sec ( +- 0.96% )
30,247,989,681 cycles # 3.747 GHz ( +- 0.52% )
14,580,011,391 instructions # 0.48 insn per cycle ( +- 0.81% )
3,063,743,405 branches # 379.523 M/sec ( +- 0.85% )
8,907,160 branch-misses # 0.29% of all branches ( +- 3.99% )
1.06150 +- 0.00427 seconds time elapsed ( +- 0.40% )
1.05041 +- 0.00176 seconds time elapsed ( +- 0.17% ) (repeat)
1.06086 +- 0.00237 seconds time elapsed ( +- 0.22% ) (repeat)
5.14.0.g79e92006-rt3-tip-rt +slub-local-lock-v2r3 full set
7,598.44 msec task-clock # 5.813 CPUs utilized ( +- 0.85% )
488,161 context-switches # 64.245 K/sec ( +- 4.29% )
196,866 cpu-migrations # 25.909 K/sec ( +- 1.49% )
13,042 page-faults # 1.716 K/sec ( +- 0.73% )
27,695,116,746 cycles # 3.645 GHz ( +- 0.79% )
18,423,934,168 instructions # 0.67 insn per cycle ( +- 0.88% )
3,969,540,695 branches # 522.415 M/sec ( +- 0.92% )
15,493,482 branch-misses # 0.39% of all branches ( +- 2.15% )
1.30709 +- 0.00890 seconds time elapsed ( +- 0.68% )
1.3205 +- 0.0134 seconds time elapsed ( +- 1.02% ) (repeat)
1.3083 +- 0.0132 seconds time elapsed ( +- 1.01% ) (repeat)
end previously reported numbers
5.14.0.gf6a71a5-rt6-tip-rt (same config, full slub set.. obviously)
7,707.63 msec task-clock # 5.880 CPUs utilized ( +- 1.46% )
562,533 context-switches # 72.984 K/sec ( +- 7.46% )
208,475 cpu-migrations # 27.048 K/sec ( +- 2.26% )
13,022 page-faults # 1.689 K/sec ( +- 0.80% )
28,025,004,779 cycles # 3.636 GHz ( +- 1.34% )
18,487,135,489 instructions # 0.66 insn per cycle ( +- 1.58% )
3,997,110,493 branches # 518.591 M/sec ( +- 1.65% )
16,078,322 branch-misses # 0.40% of all branches ( +- 4.23% )
1.3108 +- 0.0135 seconds time elapsed ( +- 1.03% )
1.2997 +- 0.0138 seconds time elapsed ( +- 1.06% ) (repeat)
1.3009 +- 0.0166 seconds time elapsed ( +- 1.28% ) (repeat)
5.14.0.gf6a71a5-rt6-tip-rt +list_lock=raw_spinlock_t
8,252.59 msec task-clock # 7.584 CPUs utilized ( +- 0.27% )
400,991 context-switches # 48.590 K/sec ( +- 6.15% )
35,979 cpu-migrations # 4.360 K/sec ( +- 5.63% )
13,261 page-faults # 1.607 K/sec ( +- 0.73% )
30,910,310,737 cycles # 3.746 GHz ( +- 0.31% )
16,522,383,240 instructions # 0.53 insn per cycle ( +- 0.92% )
3,535,219,839 branches # 428.377 M/sec ( +- 0.96% )
10,115,967 branch-misses # 0.29% of all branches ( +- 4.32% )
1.08817 +- 0.00238 seconds time elapsed ( +- 0.22% )
1.08583 +- 0.00243 seconds time elapsed ( +- 0.22% ) (repeat)
1.09003 +- 0.00164 seconds time elapsed ( +- 0.15% ) (repeat)
5.14.0.g251a152-rt6-master-rt (+SLAB_MERGE_DEFAULT,SLUB_CPU_PARTIAL,SLAB_FREELIST_RANDOM/HARDENED)
8,170.48 msec task-clock # 7.390 CPUs utilized ( +- 0.43% )
449,994 context-switches # 55.076 K/sec ( +- 4.20% )
55,912 cpu-migrations # 6.843 K/sec ( +- 4.28% )
13,144 page-faults # 1.609 K/sec ( +- 0.53% )
30,484,114,812 cycles # 3.731 GHz ( +- 0.44% )
17,554,521,787 instructions # 0.58 insn per cycle ( +- 0.76% )
3,751,725,852 branches # 459.181 M/sec ( +- 0.81% )
13,421,985 branch-misses # 0.36% of all branches ( +- 2.40% )
1.10563 +- 0.00382 seconds time elapsed ( +- 0.35% )
1.1098 +- 0.0147 seconds time elapsed ( +- 1.32% ) (repeat)
1.11308 +- 0.00883 seconds time elapsed ( +- 0.79% ) (repeat)
5.14.0.gf6a71a5-rt6-tip-rt +SLAB_MERGE_DEFAULT,SLUB_CPU_PARTIAL,SLAB_FREELIST_RANDOM/HARDENED
8,026.39 msec task-clock # 7.320 CPUs utilized ( +- 0.70% )
496,579 context-switches # 61.868 K/sec ( +- 6.78% )
65,022 cpu-migrations # 8.101 K/sec ( +- 8.29% )
13,161 page-faults # 1.640 K/sec ( +- 0.51% )
29,870,954,733 cycles # 3.722 GHz ( +- 0.67% )
17,617,522,235 instructions # 0.59 insn per cycle ( +- 1.36% )
3,760,346,459 branches # 468.498 M/sec ( +- 1.45% )
12,863,520 branch-misses # 0.34% of all branches ( +- 4.45% )
1.0965 +- 0.0103 seconds time elapsed ( +- 0.94% )
1.08149 +- 0.00362 seconds time elapsed ( +- 0.33% ) (repeat)
1.10027 +- 0.00916 seconds time elapsed ( +- 0.83% )
yup, perf delta == config delta, lets have a peek at jitter
cyclictest -Smqp99& perf stat -r100 hackbench -s4096 -l500 && killall cyclictest
5.14.0.gf6a71a5-rt6-tip-rt
SLUB+SLUB_DEBUG
T: 1 ( 5903) P:99 I:1500 C: 92330 Min: 1 Act: 2 Avg: 6 Max: 19
T: 2 ( 5904) P:99 I:2000 C: 69247 Min: 1 Act: 2 Avg: 6 Max: 21
T: 3 ( 5905) P:99 I:2500 C: 55395 Min: 1 Act: 3 Avg: 6 Max: 22
T: 4 ( 5906) P:99 I:3000 C: 46163 Min: 1 Act: 4 Avg: 7 Max: 22
T: 5 ( 5907) P:99 I:3500 C: 39568 Min: 1 Act: 3 Avg: 6 Max: 23
T: 6 ( 5909) P:99 I:4000 C: 34621 Min: 1 Act: 2 Avg: 7 Max: 22
T: 7 ( 5910) P:99 I:4500 C: 30774 Min: 1 Act: 3 Avg: 7 Max: 18
SLUB+SLUB_DEBUG+list_lock=raw_spinlock_t
T: 1 ( 4044) P:99 I:1500 C: 73340 Min: 1 Act: 3 Avg: 10 Max: 28
T: 2 ( 4045) P:99 I:2000 C: 55004 Min: 1 Act: 4 Avg: 10 Max: 33
T: 3 ( 4046) P:99 I:2500 C: 44002 Min: 1 Act: 2 Avg: 10 Max: 26
T: 4 ( 4047) P:99 I:3000 C: 36668 Min: 1 Act: 3 Avg: 10 Max: 24
T: 5 ( 4048) P:99 I:3500 C: 31429 Min: 1 Act: 3 Avg: 10 Max: 27
T: 6 ( 4049) P:99 I:4000 C: 27500 Min: 1 Act: 3 Avg: 11 Max: 30
T: 7 ( 4050) P:99 I:4500 C: 24444 Min: 1 Act: 4 Avg: 11 Max: 25
SLUB+SLUB_DEBUG+SLAB_MERGE_DEFAULT,SLUB_CPU_PARTIAL,SLAB_FREELIST_RANDOM/HARDENED
T: 1 ( 4036) P:99 I:1500 C: 74039 Min: 1 Act: 3 Avg: 9 Max: 31
T: 2 ( 4037) P:99 I:2000 C: 55528 Min: 1 Act: 3 Avg: 10 Max: 29
T: 3 ( 4038) P:99 I:2500 C: 44422 Min: 1 Act: 2 Avg: 10 Max: 31
T: 4 ( 4039) P:99 I:3000 C: 37017 Min: 1 Act: 2 Avg: 9 Max: 23
T: 5 ( 4040) P:99 I:3500 C: 31729 Min: 1 Act: 3 Avg: 10 Max: 29
T: 6 ( 4041) P:99 I:4000 C: 27762 Min: 1 Act: 2 Avg: 8 Max: 26
T: 7 ( 4042) P:99 I:4500 C: 24677 Min: 1 Act: 3 Avg: 9 Max: 27
conclusion: gee, pi both works and ain't free - ditto add more stuff=cycles :)
