On Wed, 17 May, at 12:53:50PM, Peter Zijlstra wrote:
>
> Please test..
Results are still coming in but things do look better with your patch
applied.
It does look like there's a regression when running hackbench in
process mode and when the CPUs are not fully utilised, e.g. check this
out:
hackbench-process-pipes
4.4.68 4.4.68
4.4.68 4.4.68
sles12-sp3 select-idle-cpu-aggressive
for-each-cpu-wrap-fix latest-hackbench-fix
Amean 1 0.8853 ( 0.00%) 1.2160 (-37.35%) 1.0350
(-16.91%) 1.1853 (-33.89%)
This machine has 80 CPUs and that's a 40 process workload.
Here's the key:
select-idle-cpu-aggressive: 4c77b18cf8b7 ("sched/fair: Make select_idle_cpu()
more aggressive")
for-each-cpu-wrap-fix: c743f0a5c50f ("sched/fair, cpumask: Export
for_each_cpu_wrap()")
latest-hackbench-fix: this patch
But those results definitely look to be an exception. Here's the same
machine running the same number of tasks but with pthreads,
hackbench-thread-pipes
4.4.68 4.4.68
4.4.68 4.4.68
sles12-sp3 select-idle-cpu-aggressive
for-each-cpu-wrap-fix latest-hackbench-fix
Amean 1 0.7427 ( 0.00%) 0.9760 (-31.42%) 1.1907
(-60.32%) 0.7643 ( -2.92%)
Nice win.
