Re: [PATCH 2/9] perf tools: Support the auxiliary event

[Arnaldo Carvalho de Melo]

Em Fri, Feb 05, 2021 at 09:13:34AM -0500, Liang, Kan escreveu:
> 
> 
> On 2/5/2021 5:52 AM, Namhyung Kim wrote:
> > On Wed, Feb 3, 2021 at 5:14 AM <kan.liang@xxxxxxxxxxxxxxx> wrote:
> > > 
> > > From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > > 
> > > On the Intel Sapphire Rapids server, an auxiliary event has to be
> > > enabled simultaneously with the load latency event to retrieve complete
> > > Memory Info.
> > > 
> > > Add X86 specific perf_mem_events__name() to handle the auxiliary event.
> > > - Users are only interested in the samples of the mem-loads event.
> > >    Sample read the auxiliary event.
> > > - The auxiliary event must be in front of the load latency event in a
> > >    group. Assume the second event to sample if the auxiliary event is the
> > >    leader.
> > > - Add a weak is_mem_loads_aux_event() to check the auxiliary event for
> > >    X86. For other ARCHs, it always return false.
> > > 
> > > Parse the unique event name, mem-loads-aux, for the auxiliary event.
> > > 
> > > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > > ---
> > >   tools/perf/arch/x86/util/Build        |  1 +
> > >   tools/perf/arch/x86/util/mem-events.c | 44 +++++++++++++++++++++++++++++++++++
> > >   tools/perf/util/evsel.c               |  3 +++
> > >   tools/perf/util/mem-events.c          |  5 ++++
> > >   tools/perf/util/mem-events.h          |  2 ++
> > >   tools/perf/util/parse-events.l        |  1 +
> > >   tools/perf/util/record.c              |  5 +++-
> > >   7 files changed, 60 insertions(+), 1 deletion(-)
> > >   create mode 100644 tools/perf/arch/x86/util/mem-events.c
> > > 
> > > diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
> > > index 347c39b..d73f548 100644
> > > --- a/tools/perf/arch/x86/util/Build
> > > +++ b/tools/perf/arch/x86/util/Build
> > > @@ -6,6 +6,7 @@ perf-y += perf_regs.o
> > >   perf-y += topdown.o
> > >   perf-y += machine.o
> > >   perf-y += event.o
> > > +perf-y += mem-events.o
> > > 
> > >   perf-$(CONFIG_DWARF) += dwarf-regs.o
> > >   perf-$(CONFIG_BPF_PROLOGUE) += dwarf-regs.o
> > > diff --git a/tools/perf/arch/x86/util/mem-events.c b/tools/perf/arch/x86/util/mem-events.c
> > > new file mode 100644
> > > index 0000000..11b8469
> > > --- /dev/null
> > > +++ b/tools/perf/arch/x86/util/mem-events.c
> > > @@ -0,0 +1,44 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +#include "util/pmu.h"
> > > +#include "map_symbol.h"
> > > +#include "mem-events.h"
> > > +
> > > +static char mem_loads_name[100];
> > > +static bool mem_loads_name__init;
> > > +
> > > +#define MEM_LOADS_AUX          0x8203
> > > +#define MEM_LOADS_AUX_NAME     "{cpu/mem-loads-aux/,cpu/mem-loads,ldlat=%u/pp}:S"
> > > +
> > > +bool is_mem_loads_aux_event(struct evsel *leader)
> > > +{
> > > +       if (!pmu_have_event("cpu", "mem-loads-aux"))
> > > +               return false;
> > > +
> > > +       return leader->core.attr.config == MEM_LOADS_AUX;
> > > +}
> > > +
> > > +char *perf_mem_events__name(int i)
> > > +{
> > > +       struct perf_mem_event *e = perf_mem_events__ptr(i);
> > > +
> > > +       if (!e)
> > > +               return NULL;
> > > +
> > > +       if (i == PERF_MEM_EVENTS__LOAD) {
> > > +               if (mem_loads_name__init)
> > > +                       return mem_loads_name;
> > > +
> > > +               mem_loads_name__init = true;
> > > +
> > > +               if (pmu_have_event("cpu", "mem-loads-aux")) {
> > > +                       scnprintf(mem_loads_name, sizeof(MEM_LOADS_AUX_NAME),
> > > +                                 MEM_LOADS_AUX_NAME, perf_mem_events__loads_ldlat);
> > 
> > It changes "%u" to an actual latency value, right?
> > What if the value takes 3 or more digits?
> > I'm not sure scnprintf() will handle it properly.
> > 
> 
> Yes, you are right. We should use the sizeof(mem_loads_name) as below.
> I will submit a patch to fix it.
> 
> diff --git a/tools/perf/arch/x86/util/mem-events.c
> b/tools/perf/arch/x86/util/mem-events.c
> index 11b8469..588110f 100644
> --- a/tools/perf/arch/x86/util/mem-events.c
> +++ b/tools/perf/arch/x86/util/mem-events.c
> @@ -31,7 +31,7 @@ char *perf_mem_events__name(int i)
>  		mem_loads_name__init = true;
> 
>  		if (pmu_have_event("cpu", "mem-loads-aux")) {
> -			scnprintf(mem_loads_name, sizeof(MEM_LOADS_AUX_NAME),
> +			scnprintf(mem_loads_name, sizeof(mem_loads_name),
>  				  MEM_LOADS_AUX_NAME, perf_mem_events__loads_ldlat);
>  		} else {
>  			scnprintf(mem_loads_name, sizeof(mem_loads_name),

I'll fold this in the relevant cset.

- Arnaldo