Re: [PATCH v5 07/13] perf stat: Use affinity for closing file descriptors

[Andi Kleen]

On Mon, Nov 11, 2019 at 02:30:52PM +0100, Jiri Olsa wrote:
> On Thu, Nov 07, 2019 at 10:16:40AM -0800, Andi Kleen wrote:
> > From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > 
> > Closing a perf fd can also trigger an IPI to the target CPU.
> > Use the same affinity technique as we use for reading/enabling events
> > to closing to optimize the CPU transitions.
> > 
> > Before on a large test case with 94 CPUs:
> > 
> > % time     seconds  usecs/call     calls    errors syscall
> > ------ ----------- ----------- --------- --------- ----------------
> >  32.56    3.085463          50     61483           close
> > 
> > After:
> > 
> >  10.54    0.735704          11     61485           close
> > 
> > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > 
> > ---
> > 
> > v2: Use new iterator macros
> > v3: Use new iterator macros
> > Add missing affinity__cleanup
> > v4:
> > Update iterators again
> > ---
> >  tools/perf/util/evlist.c | 27 +++++++++++++++++++++++++--
> >  1 file changed, 25 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index dae6e846b2f8..0dcea66329e2 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -18,6 +18,7 @@
> >  #include "debug.h"
> >  #include "units.h"
> >  #include <internal/lib.h> // page_size
> > +#include "affinity.h"
> >  #include "../perf.h"
> >  #include "asm/bug.h"
> >  #include "bpf-event.h"
> > @@ -1169,9 +1170,31 @@ void perf_evlist__set_selected(struct evlist *evlist,
> >  void evlist__close(struct evlist *evlist)
> >  {
> >  	struct evsel *evsel;
> > +	struct affinity affinity;
> > +	int cpu, i;
> >  
> > -	evlist__for_each_entry_reverse(evlist, evsel)
> > -		evsel__close(evsel);
> > +	if (!evlist->core.cpus) {
> 
> should this be evlist->all_cpus?

This detects perf record essentially. I had some problems with perf record
in early testing, so I just disabled it, since I was just focussing
on stat. all_cpus would be set for perf record too.

-Andi