Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath

[Michal Hocko]

On Wed 27-07-16 14:16:22, Rik van Riel wrote:
> On Wed, 2016-07-27 at 18:33 +0200, Michal Hocko wrote:
> > On Wed 27-07-16 10:47:59, Janani Ravichandran wrote:
> > > 
> > > Add tracepoints to the slowpath code to gather some information.
> > > The tracepoints can also be used to find out how much time was
> > > spent in
> > > the slowpath.
> > I do not think this is a right thing to measure.
> > __alloc_pages_slowpath
> > is more a code organization thing. The fast path might perform an
> > expensive operations like zone reclaim (if node_reclaim_mode > 0) so
> > these trace point would miss it.
> 
> It doesn't look like it does. The fast path either
> returns an allocated page to the caller, or calls
> into the slow path.

I must be missing something here but what prevents
__alloc_pages_nodemask->get_page_from_freelist from doing zone_reclaim?
-- 
Michal Hocko
SUSE Labs