Messages in this thread | | | Subject | Re: [PATCH] sched/fair: provide u64 read for 32-bits arch helper | From | Lukasz Luba <> | Date | Tue, 28 Jul 2020 10:09:29 +0100 |
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Hi Vincent,
On 7/27/20 11:59 AM, vincent.donnefort@arm.com wrote: > From: Vincent Donnefort <vincent.donnefort@arm.com> > > Introducing two macro helpers u64_32read() and u64_32read_set_copy() to > factorize the u64 vminruntime and last_update_time read on a 32-bits > architecture. Those new helpers encapsulate smp_rmb() and smp_wmb() > synchronization and therefore, have a small penalty in set_task_rq_fair() > and init_cfs_rq(). > > The choice of using a macro over an inline function is driven by the > conditional u64 variable copy declarations. > > #ifndef CONFIG_64BIT > u64 [vminruntime|last_update_time]_copy; > #endif > > Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> >
I've run it on 32-bit ARM big.LITTLE platform (odroid xu3) with the CONFIG_FAIR_GROUP_SCHED and CONFIG_CGROUP_SCHED.
I haven't observed any issues while running hackbench or booting the kernel, the performance of affected function set_task_rq_fair() is the same.
Function profile results after hackbench test: --------w/ Vincent's patch + performance cpufreq gov------------ root@odroid:/sys/kernel/debug/tracing# cat trace_stat/function? Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 4068 3753.185 us 0.922 us 1.239 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 4492 4180.133 us 0.930 us 2.318 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 4208 3991.386 us 0.948 us 13.552 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 4753 4432.231 us 0.932 us 5.875 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 7980 5037.096 us 0.631 us 1.690 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 8143 5078.515 us 0.623 us 2.930 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 9721 6477.904 us 0.666 us 2.425 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 7743 4896.002 us 0.632 us 1.188 us
-----------w/o Vincent patch, performance cpufreq gov------------ root@odroid:/sys/kernel/debug/tracing# cat trace_stat/function? Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 6525 5830.450 us 0.893 us 3.213 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 6646 6069.444 us 0.913 us 9.651 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 5988 5646.133 us 0.942 us 7.685 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 5883 5390.103 us 0.916 us 29.283 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 3844 2561.186 us 0.666 us 0.933 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 5515 3491.011 us 0.633 us 9.845 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 6947 4808.522 us 0.692 us 5.822 us Function Hit Time Avg s^2 -------- --- ---- --- --- set_task_rq_fair 4530 2810.000 us 0.620 us 0.554 us
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Regards, Lukasz
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