On Thu, 10 Dec 2015 14:45:02 -0600 (CST) Christoph Lameter <[email protected]> wrote:
> Currently the vmstat updater is not deferrable as a result of commit > ba4877b9ca51f80b5d30f304a46762f0509e1635. This in turn can cause multiple > interruptions of the applications because the vmstat updater may run at > different times than tick processing. No good. > > Make vmstate_update deferrable again and provide a function that > folds the differentials when the processor is going to idle mode thus > addressing the issue of the above commit in a clean way. > > Note that the shepherd thread will continue scanning the differentials > from another processor and will reenable the vmstat workers if it > detects any changes. > > Fixes: ba4877b9ca51f80b5d30f304a46762f0509e1635 (do not use deferrable delay) > Signed-off-by: Christoph Lameter <[email protected]> > > ... > > /* > + * Switch off vmstat processing and then fold all the remaining differentials > + * until the diffs stay at zero. The function is used by NOHZ and can only be > + * invoked when tick processing is not active. > + */ > +void quiet_vmstat(void) > +{ > + do { > + if (!cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off)) > + cancel_delayed_work(this_cpu_ptr(&vmstat_work)); > + > + } while (refresh_cpu_vm_stats(false)); > +} How do we know this will terminate in a reasonable amount of time if other CPUs are pounding away? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
