Hi, Frederic! >>>>> On Mon, 29 Jan 2018 02:10:26 +0100, Frederic Weisbecker wrote: > On Wed, Jan 24, 2018 at 10:46:08AM -0500, Luiz Capitulino wrote:
[...] >> Since the 1Hz tick offload worked for you, I must be missing >> a way to disable this timer or the kernel is thinking my CPU >> has unstable TSC (which it doesn't AFAIK). > It's beyond the scope of this patchset but indeed that's > right, I run my kernels with tsc=reliable because my CPUs > don't have the TSC_RELIABLE flag. That's the only way I found > to shutdown the tick completely on my test machine, otherwise > I keep having that clocksource watchdog. [...] Thanks, it helps. But I have accounting problem: if I run user busy loop on the nohz cpu, the task accounting works correctly (top shows the task takes 100% cpu), but cpu accounting is wrong (cpu is 100% idle, in the per-core view as well). If I understand correctly, the stats are updated by account_user_time() -> task_group_account_field() but there is no call for it in case of offloading (it is called from irqtime_account_process_tick, account_process_tick, vtime_user_exit). Moreover, task_group_account_field() uses __this_cpu_add() which will be wrong for offloading. For testing I used kcpustat_cpu(task_cpu(p)) in task_group_account_field() and added call account_user_time(curr, delta) to the sched_tick_remote() what fixes it for me, but what would be the proper fix? -- WBR, Yauheni Kaliuta
