Messages in this thread | | | Date | Fri, 2 Jul 2021 10:00:11 +0200 (CEST) | From | Christoph Lameter <> | Subject | Re: [patch 0/5] optionally sync per-CPU vmstats counter on return to userspace |
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On Thu, 1 Jul 2021, Marcelo Tosatti wrote:
> The logic to disable vmstat worker thread, when entering > nohz full, does not cover all scenarios. For example, it is possible > for the following to happen: > > 1) enter nohz_full, which calls refresh_cpu_vm_stats, syncing the stats. > 2) app runs mlock, which increases counters for mlock'ed pages. > 3) start -RT loop > > Since refresh_cpu_vm_stats from nohz_full logic can happen _before_ > the mlock, vmstat shepherd can restart vmstat worker thread on > the CPU in question.
Can we enter nohz_full after the app runs mlock?
> To fix this, optionally sync the vmstat counters when returning > from userspace, controllable by a new "vmstat_sync" isolcpus > flags (default off). > > See individual patches for details.
Wow... This is going into some performance sensitive VM counters here and adds code to their primitives.
Isnt there a simpler solution that does not require this amount of changes?
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