On Fri 08-05-20 15:25:16, Feng Tang wrote: > percpu_counter_sum_positive() will provide more accurate info.
Why do we need that? > Its time cost is about 800 nanoseconds on a 2C/4T platform and > 2~3 microseconds on a 2S/36C/72T server in normal case, and in > worst case where vm_committed_as's spinlock is under severe > contention, it costs 30~40 microseconds for the 2S/36C/72T sever, > which should be fine for its two users: /proc/meminfo and HV ballon > driver's status trace per second. OK, this explains that the additional overhead is not terrible but there is no actual information on why the imprecision is a problem. > Signed-off-by: Feng Tang <[email protected]> > --- > mm/util.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/util.c b/mm/util.c > index 988d11e..3de78e9 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -774,7 +774,7 @@ struct percpu_counter vm_committed_as > ____cacheline_aligned_in_smp; > */ > unsigned long vm_memory_committed(void) > { > - return percpu_counter_read_positive(&vm_committed_as); > + return percpu_counter_sum_positive(&vm_committed_as); > } > EXPORT_SYMBOL_GPL(vm_memory_committed); > > -- > 2.7.4 -- Michal Hocko SUSE Labs
