Re: [GIT PULL||RFC 00/11] perf library and regression testing improvements

Stephane Eranian
2011-01-04T14:59:41Z

The issue is related to a mismatch in the data structure layout
between builtin-stat.c and util/evsel.c. The offset of the counts fields
is different between the two files. Getting closer.....

On Tue, Jan 4, 2011 at 3:46 PM, Stephane Eranian <eranian@google.com> wrote:
> On Tue, Jan 4, 2011 at 3:36 PM, Arnaldo Carvalho de Melo
> <acme@infradead.org> wrote:
>> Em Tue, Jan 04, 2011 at 03:33:38PM +0100, Stephane Eranian escreveu:
>>> No improvement with this patch.
>>
>> I was guessing you were using it somehow without calling
>> perf_evsel__alloc_counts, now I guess you're just using what is in
>> tip/perf/core, no local changes, right?
>>
> I am using:
> git://git.eu.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-tip.git
>
>> Next step: there are anonymous structs inside anonymous unions, what
>> compiler/distro?
> Yes, I am looking at those right now.
>>
> gcc 4.4.3 or gcc 4.2.4 (ubuntu hardy or 10.04).
>
>> - Arnaldo
>>
>>> On Tue, Jan 4, 2011 at 3:27 PM, Arnaldo Carvalho de Melo
>>> <acme@infradead.org> wrote:
>>> > Em Tue, Jan 04, 2011 at 12:19:58PM -0200, Arnaldo Carvalho de Melo escreveu:
>>> >> Em Tue, Jan 04, 2011 at 03:09:08PM +0100, Stephane Eranian escreveu:
>>> >> > Arnaldo,
>>> >> > Looks like what's wrong is not ps but count:
>>> >> >
>>> >> > Program received signal SIGSEGV, Segmentation fault.
>>> >> > [Switching to Thread 0x7f96967fd6e0 (LWP 5156)]
>>> >> > 0x0000000000412b58 in read_counter_aggr (counter=0x7d4820) at builtin-stat.c:206
>>> >> > 206                 update_stats(&ps->res_stats[i], count[i]);
>>> >> > (gdb) print ps
>>> >> > $1 = (struct perf_stat *) 0x7d48a0
>>> >> > (gdb) print *ps
>>> >> > $2 = {res_stats = {{n = 0, mean = 0, M2 = 0}, {n = 0, mean = 0, M2 =
>>> >> > 0}, {n = 0, mean = 0, M2 = 0}}}
>>> >> > (gdb) print count
>>> >> > $3 = (u64 *) 0x12
>>> >> > (gdb) print *count
>>> >> > Cannot access memory at address 0x12
>>> >> > (gdb) print count
>>> >> > $4 = (u64 *) 0x12
>>> >>
>>> >> Count is:
>>> >>
>>> >> u64 *count = counter->counts->aggr.values;
>>> >
>>> > Can you try with this patch?
>>> >
>>> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>>> > index 02b2d80..7876b11 100644
>>> > --- a/tools/perf/builtin-stat.c
>>> > +++ b/tools/perf/builtin-stat.c
>>> > @@ -196,12 +196,14 @@ static inline int nsec_counter(struct perf_evsel *evsel)
>>> >  static int read_counter_aggr(struct perf_evsel *counter)
>>> >  {
>>> >        struct perf_stat *ps = counter->priv;
>>> > -       u64 *count = counter->counts->aggr.values;
>>> > +       u64 *count;
>>> >        int i;
>>> >
>>> >        if (__perf_evsel__read(counter, cpus->nr, threads->nr, scale) < 0)
>>> >                return -1;
>>> >
>>> > +       count = counter->counts->aggr.values;
>>> > +
>>> >        for (i = 0; i < 3; i++)
>>> >                update_stats(&ps->res_stats[i], count[i]);
>>> >
>>> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>>> > index d337761..26962ea 100644
>>> > --- a/tools/perf/util/evsel.c
>>> > +++ b/tools/perf/util/evsel.c
>>> > @@ -89,8 +89,12 @@ int __perf_evsel__read(struct perf_evsel *evsel,
>>> >  {
>>> >        size_t nv = scale ? 3 : 1;
>>> >        int cpu, thread;
>>> > -       struct perf_counts_values *aggr = &evsel->counts->aggr, count;
>>> > +       struct perf_counts_values *aggr, count;
>>> >
>>> > +       if (evsel->counts == NULL && perf_evsel__alloc_counts(evsel, ncpus) < 0)
>>> > +               return -ENOMEM;
>>> > +
>>> > +       aggr = &evsel->counts->aggr;
>>> >        aggr->val = 0;
>>> >
>>> >        for (cpu = 0; cpu < ncpus; cpu++) {
>>> >
>>
>