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    SubjectRe: [PATCH 2/5] perf unwind: Do not look at globals
    Em Tue, Jan 16, 2018 at 08:49:09PM +0100, Jiri Olsa escreveu:
    > On Tue, Jan 16, 2018 at 03:26:50PM -0300, Arnaldo Carvalho de Melo wrote:
    >
    > SNIP
    >
    > > diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
    > > index c0debc3f79b6..c0815a37fdb5 100644
    > > --- a/tools/perf/builtin-c2c.c
    > > +++ b/tools/perf/builtin-c2c.c
    > > @@ -2390,9 +2390,10 @@ static int setup_callchain(struct perf_evlist *evlist)
    > > enum perf_call_graph_mode mode = CALLCHAIN_NONE;
    > >
    > > if ((sample_type & PERF_SAMPLE_REGS_USER) &&
    > > - (sample_type & PERF_SAMPLE_STACK_USER))
    > > + (sample_type & PERF_SAMPLE_STACK_USER)) {
    > > mode = CALLCHAIN_DWARF;
    > > - else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
    > > + dwarf_callchain_users = true;
    > > + } else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
    > > mode = CALLCHAIN_LBR;
    > > else if (sample_type & PERF_SAMPLE_CALLCHAIN)
    > > mode = CALLCHAIN_FP;
    > > diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
    > > index dd4df9a5cd06..6593779224d5 100644
    > > --- a/tools/perf/builtin-report.c
    > > +++ b/tools/perf/builtin-report.c
    > > @@ -338,9 +338,10 @@ static int report__setup_sample_type(struct report *rep)
    > >
    > > if (symbol_conf.use_callchain || symbol_conf.cumulate_callchain) {
    > > if ((sample_type & PERF_SAMPLE_REGS_USER) &&
    > > - (sample_type & PERF_SAMPLE_STACK_USER))
    > > + (sample_type & PERF_SAMPLE_STACK_USER)) {
    > > callchain_param.record_mode = CALLCHAIN_DWARF;
    > > - else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
    > > + dwarf_callchain_users = true;
    > > + } else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
    > > callchain_param.record_mode = CALLCHAIN_LBR;
    > > else
    > > callchain_param.record_mode = CALLCHAIN_FP;
    > > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
    > > index c1cce474c0f1..08bc818f371b 100644
    > > --- a/tools/perf/builtin-script.c
    > > +++ b/tools/perf/builtin-script.c
    > > @@ -2919,9 +2919,10 @@ static void script__setup_sample_type(struct perf_script *script)
    > >
    > > if (symbol_conf.use_callchain || symbol_conf.cumulate_callchain) {
    > > if ((sample_type & PERF_SAMPLE_REGS_USER) &&
    > > - (sample_type & PERF_SAMPLE_STACK_USER))
    > > + (sample_type & PERF_SAMPLE_STACK_USER)) {
    > > callchain_param.record_mode = CALLCHAIN_DWARF;
    > > - else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
    > > + dwarf_callchain_users = true;
    > > + } else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
    > > callchain_param.record_mode = CALLCHAIN_LBR;
    > > else
    > > callchain_param.record_mode = CALLCHAIN_FP;
    > > diff --git a/tools/perf/tests/dwarf-unwind.c b/tools/perf/tests/dwarf-unwind.c
    > > index ac40e05bcab4..260418969120 100644
    > > --- a/tools/perf/tests/dwarf-unwind.c
    > > +++ b/tools/perf/tests/dwarf-unwind.c
    > > @@ -173,6 +173,7 @@ int test__dwarf_unwind(struct test *test __maybe_unused, int subtest __maybe_unu
    > > }
    > >
    > > callchain_param.record_mode = CALLCHAIN_DWARF;
    > > + dwarf_callchain_users = true;
    > >
    > > if (init_live_machine(machine)) {
    > > pr_err("Could not init machine\n");
    > > diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
    > > index 082505d08d72..32ef7bdca1cf 100644
    > > --- a/tools/perf/util/callchain.c
    > > +++ b/tools/perf/util/callchain.c
    > > @@ -37,6 +37,15 @@ struct callchain_param callchain_param = {
    > > CALLCHAIN_PARAM_DEFAULT
    > > };
    > >
    > > +/*
    > > + * Are there any events usind DWARF callchains?
    > > + *
    > > + * I.e.
    > > + *
    > > + * -e cycles/call-graph=dwarf/
    > > + */
    > > +bool dwarf_callchain_users;
    >
    > hum, I don't follow.. this bool seems to mirror the usage of
    > 'param->record_mode = CALLCHAIN_DWARF', whats the difference?
    >
    > also, the patch title says 'Do not look at globals', while inside you

    The first version didn't look at globals, the second one doesn't look at
    an _specific_ global variable, the global config for --call-graph, which
    is a global variable, callchain_param, which _we_ can't touch at
    apply_config_terms(), since that is about _just_ that event, not all of
    them.

    > add new global dwarf_callchain_users and work with it.. what do I miss?
    >
    > I'll check tomorrow with clean head ;-)

    Look closely at apply_config_terms() it passes a _local_ variable to

    perf_evsel__config_callchain(evsel, opts, &param);

    It will not affect any globals that tools/perf/util/unwind-libunwind-local.c
    could possibly use... and that is the problem. :-)

    The right fix, as I said, is more involved and may allow us to remove
    these two global variables, both callchain_param and
    dwarf_callchain_users.

    We need to have per-evsel unwind ops, per thread addr_space continues to
    be used by the dwarf unwinder _for the events sampled in that thread_,
    etc.

    The prepare_unwind is to be made to evsel and thread (for thread we need
    to look at one of its executable maps, to determine if it is 32-bit or
    64-bit, etc, but not necessarily at that insert_map part, etc).

    - Arnaldo

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