Messages in this thread | | | Subject | Re: [patch 2/4] task isolation: sync vmstats on return to userspace | From | nsaenzju@redhat ... | Date | Tue, 03 Aug 2021 17:13:03 +0200 |
| |
On Fri, 2021-07-30 at 17:18 -0300, 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. > > To fix this, use the task isolation prctl interface to quiesce > deferred actions when returning to userspace.
Even though this is mostly targeted at nohz_full users, I believe I haven't seen anything in this series that forces the feature to be run on nohz_full CPUs (this is a good thing IMO). So, I'd suggest to reword the patch description so it doesn't imply nohz_full is necessary to use this.
-- Nicolás Sáenz
| |