Re: [PATCH] mm: vmscan: add tracepoints for node reclaim

[Michal Hocko <mhocko@kernel.org>]

On Thu 28-02-19 18:20:16, Yafang Shao wrote:
> On Thu, Feb 28, 2019 at 6:17 PM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > On Thu 28-02-19 16:14:24, Yafang Shao wrote:
> > > In the page alloc fast path, it may do node reclaim, which may cause
> > > latency spike.
> > > We should add tracepoint for this event, and also mesure the latency
> > > it causes.
> > >
> > > So bellow two tracepoints are introduced,
> > >       mm_vmscan_node_reclaim_begin
> > >       mm_vmscan_node_reclaim_end
> >
> > This makes some sense to me. Regular direct reclaim already does have
> > similar tracepoints. Is there any reason you haven't used
> > mm_vmscan_direct_reclaim_{begin,end}_template as all other direct reclaim
> > paths?
> >
> 
> Because I also want to know the node id, which is not show in
> mm_vmscan_direct_reclaim_{begin,end}_template.
> 
> Or should we modify mm_vmscan_direct_reclaim_{begin,end}_template to
> show the node id as well ?

OK, I see. I thought it was there but it would make much less sense than
for the node reclaim for sure. A separate tracepoint makes more sense
then.
-- 
Michal Hocko
SUSE Labs