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+--- Thread: Help with linux task schuduler at 4.18, please (/showthread.php?tid=6590)
Help with linux task schuduler at 4.18, please - dukla2000 - 09-25-2018
Hi all
Is there anyone here who understands how to "tune" the Linux task scheduler? My problem is that at 4.18.9 it does not obviously favour the big cores for CPU heavy jobs which is crazy.
I wrote a little script to demonstrate what I mean - it uses an additional package stress as an example that can spawn n jobs for t seconds. In my case I run the load for 10 seconds, and after 5 seconds have a look which CPUs are in use:
Code:
stress -c 1 -t 10 &
sleep 5
ps -L -o pid,lwp,pcpu,cpuid,time
sleep 6
stress -c 2 -t 10 &
sleep 5
ps -L -o pid,lwp,pcpu,cpuid,time
sleep 6
stress -c 3 -t 10 &
sleep 5
ps -o pid,lwp,pcpu,cpuid,time
sleep 6
stress -c 4 -t 10 &
sleep 5
ps -L -o pid,lwp,pcpu,cpuid,timeOn the 4.4.138 (Ayufan) kernel things are pretty much to be expected - CPUs 4 & 5 (the big A72 cores) are always used:
Code:
$ ./testcpu
stress: info: [1043] dispatching hogs: 1 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
741 741 0.0 4 00:00:00
1042 1042 0.0 0 00:00:00
1043 1043 0.0 4 00:00:00
1045 1045 100 4 00:00:05
1047 1047 0.0 5 00:00:00
stress: info: [1043] successful run completed in 10s
stress: info: [1050] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
741 741 0.0 4 00:00:00
1042 1042 0.0 5 00:00:00
1050 1050 0.0 5 00:00:00
1052 1052 98.6 5 00:00:04
1053 1053 100 4 00:00:05
1055 1055 0.0 0 00:00:00
stress: info: [1050] successful run completed in 10s
stress: info: [1058] dispatching hogs: 3 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
741 741 0.0 4 00:00:00
1042 1042 0.0 5 00:00:00
1058 1058 0.0 4 00:00:00
1060 1060 99.8 0 00:00:04
1061 1061 100 5 00:00:05
1062 1062 100 4 00:00:05
1064 1064 0.0 3 00:00:00
stress: info: [1058] successful run completed in 10s
stress: info: [1067] dispatching hogs: 4 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
741 741 0.0 4 00:00:00
1042 1042 0.0 4 00:00:00
1067 1067 0.0 2 00:00:00
1069 1069 100 1 00:00:05
1070 1070 100 4 00:00:05
1071 1071 100 3 00:00:05
1072 1072 100 5 00:00:05
1074 1074 0.0 0 00:00:00
stress: info: [1067] successful run completed in 10sOn 4.18.9 (despite all my efforts configuring the kernel) it is more luck whether CPUs 4 or 5 do any work:
Code:
$ ./testcpu
stress: info: [2375] dispatching hogs: 1 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2354 2354 0.1 3 00:00:00
2374 2374 0.0 0 00:00:00
2375 2375 0.0 4 00:00:00
2377 2377 83.5 2 00:00:05
2379 2379 1.0 5 00:00:00
stress: info: [2375] successful run completed in 10s
stress: info: [2382] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2354 2354 0.0 3 00:00:00
2374 2374 0.0 0 00:00:00
2382 2382 0.0 1 00:00:00
2384 2384 100 3 00:00:05
2385 2385 100 4 00:00:05
2387 2387 0.0 0 00:00:00
stress: info: [2382] successful run completed in 10s
stress: info: [2390] dispatching hogs: 3 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2354 2354 0.0 3 00:00:00
2374 2374 0.0 1 00:00:00
2390 2390 0.0 4 00:00:00
2392 2392 100 3 00:00:05
2393 2393 100 5 00:00:05
2394 2394 100 2 00:00:05
2396 2396 0.0 0 00:00:00
stress: info: [2390] successful run completed in 10s
stress: info: [2399] dispatching hogs: 4 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2354 2354 0.0 3 00:00:00
2374 2374 0.0 3 00:00:00
2399 2399 0.0 5 00:00:00
2401 2401 100 0 00:00:05
2402 2402 100 4 00:00:05
2403 2403 100 5 00:00:05
2404 2404 100 2 00:00:05
2406 2406 0.0 1 00:00:00
stress: info: [2399] successful run completed in 10sThere does seem to be a kernel CONFIG option at 4.4, ARM_ROCKCHIP_CPUFREQ, that could explain the 4.4 behaviour. And is not available at 4.18.9. But in reality I would expect stock/mainline 4.18 scheduling to cope properly with big.LITTLE CPUs?
Any thoughts/suggestions welcomed.
RE: Help with linux task schuduler at 4.18, please - dukla2000 - 10-02-2018
Same problem with 4.19.0-rc4, with 1 hog it runs on an A53 core (CPU 1), with 3 hogs two are on A53s and only 1 on an A72 (CPU 4):
Code:
$ uname -a
Linux rpro64.dukla.net 4.19.0-rc4-1071-ayufan-g10a63ec6c2a2 #1 SMP PREEMPT Mon Oct 1 07:33:40 UTC 2018 aarch64 aarch64 aarch64 GNU/Linux
chris@rpro64:~/bin/Rpro64$ ./testcpu
stress: info: [3067] dispatching hogs: 1 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2736 2736 0.0 2 00:00:00
3066 3066 0.0 3 00:00:00
3067 3067 0.0 4 00:00:00
3069 3069 100 1 00:00:05
3071 3071 0.0 4 00:00:00
stress: info: [3067] successful run completed in 10s
stress: info: [3075] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2736 2736 0.0 2 00:00:00
3066 3066 0.0 1 00:00:00
3075 3075 0.0 4 00:00:00
3077 3077 100 4 00:00:05
3078 3078 100 0 00:00:05
3081 3081 0.0 1 00:00:00
stress: info: [3075] successful run completed in 10s
stress: info: [3085] dispatching hogs: 3 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2736 2736 0.0 2 00:00:00
3066 3066 0.0 2 00:00:00
3085 3085 0.0 4 00:00:00
3087 3087 98.4 3 00:00:04
3088 3088 98.4 4 00:00:04
3089 3089 98.4 0 00:00:04
3091 3091 0.0 2 00:00:00
stress: info: [3085] successful run completed in 10s
stress: info: [3094] dispatching hogs: 4 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
2736 2736 0.0 2 00:00:00
3066 3066 0.0 4 00:00:00
3094 3094 0.0 2 00:00:00
3096 3096 98.8 4 00:00:04
3097 3097 98.6 5 00:00:04
3098 3098 98.8 1 00:00:04
3099 3099 99.0 2 00:00:04
3101 3101 0.0 3 00:00:00RE: Help with linux task schuduler at 4.18, please - hunderteins - 10-05-2018
on 4.4 when turning off CONFIG_ARM_ROCKCHIP_CPUFREQ and
setting CONFIG_ARM_BIG_LITTLE_CPUFREQ
I get the same cpu-core preference for cpu4 and cpu5 (A72)
Is this set on your 4.19?
Code:
#
# CPU frequency scaling drivers
#
CONFIG_CPUFREQ_DT=y
CONFIG_ARM_BIG_LITTLE_CPUFREQ=y
CONFIG_ARM_DT_BL_CPUFREQ=y
# CONFIG_ARM_KIRKWOOD_CPUFREQ is not set
# CONFIG_ARM_ROCKCHIP_CPUFREQ is not setCode:
$ ./testcpu
stress: info: [1561] dispatching hogs: 1 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
1475 1475 0.0 4 00:00:00
1560 1560 0.0 4 00:00:00
1561 1561 0.0 1 00:00:00
1563 1563 100 5 00:00:05
1564 1564 0.0 4 00:00:00
stress: info: [1561] successful run completed in 10s
stress: info: [1566] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
1475 1475 0.0 4 00:00:00
1560 1560 0.0 0 00:00:00
1566 1566 0.0 4 00:00:00
1568 1568 99.6 5 00:00:04
1569 1569 99.8 4 00:00:04
1570 1570 0.0 1 00:00:00
stress: info: [1566] successful run completed in 10s
stress: info: [1572] dispatching hogs: 3 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
1475 1475 0.0 4 00:00:00
1560 1560 0.0 0 00:00:00
1572 1572 0.0 1 00:00:00
1574 1574 100 4 00:00:05
1575 1575 100 3 00:00:05
1576 1576 100 5 00:00:05
1577 1577 0.0 1 00:00:00
stress: info: [1572] successful run completed in 10s
stress: info: [1580] dispatching hogs: 4 cpu, 0 io, 0 vm, 0 hdd
PID LWP %CPU CPUID TIME
1475 1475 0.0 4 00:00:00
1560 1560 0.0 3 00:00:00
1580 1580 0.0 4 00:00:00
1582 1582 100 5 00:00:05
1583 1583 99.8 1 00:00:04
1584 1584 100 4 00:00:05
1585 1585 100 2 00:00:05
1586 1586 0.0 0 00:00:00
stress: info: [1580] successful run completed in 10sRE: Help with linux task schuduler at 4.18, please - dukla2000 - 10-06-2018
(10-05-2018, 03:20 AM)hunderteins Wrote: on 4.4 when turning off CONFIG_ARM_ROCKCHIP_CPUFREQ and
setting CONFIG_ARM_BIG_LITTLE_CPUFREQ
I get the same cpu-core preference for cpu4 and cpu5 (A72)
Is this set on your 4.19?
That is really interesting, thanks.
On both 4.18 and 4.18 I have tried both BIG_LITTLE_CPUFREQ and BL_CPUFREQ
Code:
#
# CPU frequency scaling drivers
#
CONFIG_CPUFREQ_DT=y
CONFIG_CPUFREQ_DT_PLATDEV=y
# CONFIG_ACPI_CPPC_CPUFREQ is not set
CONFIG_ARM_BIG_LITTLE_CPUFREQ=y
CONFIG_ARM_DT_BL_CPUFREQ=y
# CONFIG_ARM_SCPI_CPUFREQ is not set
# CONFIG_QORIQ_CPUFREQ is not set
CONFIG_NET=y
CONFIG_NET_INGRESS=ywith no success. My thinking is that by now big.LITTLE is old enough that mainline support should be there. But I still cannot discover what I have "wrong".