Re: [PATCH v6 03/10] perf/x86/rapl: Remove the cpu_to_rapl_pmu() function

["Zhang, Rui" <rui.zhang@intel.com>]

On Mon, 2024-11-04 at 08:45 +0530, Dhananjay Ugwekar wrote:
> Hello Rui,
> 
> Thanks for reviewing and testing the series!,
> 
> On 11/1/2024 1:36 PM, Zhang, Rui wrote:
> > On Mon, 2024-10-28 at 14:49 +0530, Dhananjay Ugwekar wrote:
> > > Hello Gautham,
> > > 
> > > On 10/28/2024 2:23 PM, Gautham R. Shenoy wrote:
> > > > Hello Dhananjay,
> > > > 
> > > > On Fri, Oct 25, 2024 at 11:13:41AM +0000, Dhananjay Ugwekar
> > > > wrote:
> > > > > Prepare for the addition of RAPL core energy counter support.
> > > > > Post which, one CPU might be mapped to more than one rapl_pmu
> > > > > (package/die one and a core one). So, remove the
> > > > > cpu_to_rapl_pmu()
> > > > > function.
> > > > > 
> > > > > Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
> > > > > ---
> > > > >  arch/x86/events/rapl.c | 19 ++++++-------------
> > > > >  1 file changed, 6 insertions(+), 13 deletions(-)
> > > > > 
> > > > > diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
> > > > > index f70c49ca0ef3..d20c5b1dd0ad 100644
> > > > > --- a/arch/x86/events/rapl.c
> > > > > +++ b/arch/x86/events/rapl.c
> > > > > @@ -162,17 +162,6 @@ static inline unsigned int
> > > > > get_rapl_pmu_idx(int cpu)
> > > > >                                         
> > > > > topology_logical_die_id(cpu);
> > > > >  }
> > > > >  
> > > > > -static inline struct rapl_pmu *cpu_to_rapl_pmu(unsigned int
> > > > > cpu)
> > > > > -{
> > > > > -       unsigned int rapl_pmu_idx = get_rapl_pmu_idx(cpu);
> > > > > -
> > > > > -       /*
> > > > > -        * The unsigned check also catches the '-1' return
> > > > > value
> > > > > for non
> > > > > -        * existent mappings in the topology map.
> > > > > -        */
> > > > 
> > > > 
> > > > See the comment here why rapl_pmu_idx should be an "unsigned
> > > > int".
> > > > 
> > > > 
> > > > > -       return rapl_pmu_idx < rapl_pmus->nr_rapl_pmu ?
> > > > > rapl_pmus-
> > > > > > pmus[rapl_pmu_idx] : NULL;
> > > > > -}
> > > > > -
> > > > >  static inline u64 rapl_read_counter(struct perf_event
> > > > > *event)
> > > > >  {
> > > > >         u64 raw;
> > > > > @@ -348,7 +337,7 @@ static void rapl_pmu_event_del(struct
> > > > > perf_event *event, int flags)
> > > > >  static int rapl_pmu_event_init(struct perf_event *event)
> > > > >  {
> > > > >         u64 cfg = event->attr.config & RAPL_EVENT_MASK;
> > > > > -       int bit, ret = 0;
> > > > > +       int bit, rapl_pmu_idx, ret = 0;
> > > > 
> > > > Considering that, shouldn't rapl_pmu_idx be an "unsigned int"
> > > > no?
> > > 
> > > Correct, with unsigned int we will be able to check for negative
> > > values as well with the 
> > > "if (rapl_pmu_idx >= rapl_pmus->nr_rapl_pmu)" check. Will fix
> > > this in
> > > next version.
> > > 
> > you can stick with unsigned int here, but in patch 10/10, IMO,
> > making
> > get_rapl_pmu_idx() return int instead of unsigned int is more
> > straightforward.
> 
> But I have one doubt, there wont be any functional difference in
> returning 
> "unsigned int" vs "int" right?

yes, this doesn't cause any issue.

> , we will still need to check the same condition 
> for the return value i.e. "if (rapl_pmu_idx >= rapl_pmus-
> >nr_rapl_pmu)" 
> (assuming we are still storing the return value in "unsigned int
> rapl_pmu_idx"), 
> I think I didnt get your point.

With this patch, below comment is removed
 /*
  * The unsigned check also catches the '-1' return
value for non
  * existent mappings in the topology map.
  */
And we still rely on the unsigned int -> int conversion for the error
check.

So IMO, we should either add back a similar comment, or convert
get_rapl_pmu_idx() to return int and modify the error check.

thanks,
rui


> Thanks,
> Dhananjay
> 
> > 
> > thanks,
> > rui
> > 
> > > Thanks,
> > > Dhananjay
> > > 
> > > > 
> > > > --
> > > > Thanks and Regards
> > > > gautham.
> > > > 
> > > > 
> > > > >         struct rapl_pmu *pmu;
> > > > >  
> > > > >         /* only look at RAPL events */
> > > > > @@ -376,8 +365,12 @@ static int rapl_pmu_event_init(struct
> > > > > perf_event *event)
> > > > >         if (event->attr.sample_period) /* no sampling */
> > > > >                 return -EINVAL;
> > > > >  
> > > > > +       rapl_pmu_idx = get_rapl_pmu_idx(event->cpu);
> > > > > +       if (rapl_pmu_idx >= rapl_pmus->nr_rapl_pmu)
> > > > > +               return -EINVAL;
> > > > > +
> > > > >         /* must be done before validate_group */
> > > > > -       pmu = cpu_to_rapl_pmu(event->cpu);
> > > > > +       pmu = rapl_pmus->pmus[rapl_pmu_idx];
> > > > >         if (!pmu)
> > > > >                 return -EINVAL;
> > > > >         event->pmu_private = pmu;
> > > > > -- 
> > > > > 2.34.1
> > > > > 
> >