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    SubjectRe: [PATCH v4 12/18] perf: add support for sampling taken branch to perf record
    On Saturday 28 January 2012 02:26 AM, Stephane Eranian wrote:
    > From: Roberto Agostino Vitillo <ravitillo@lbl.gov>
    >
    > This patch adds a new option to enable taken branch stack
    > sampling, i.e., leverage the PERF_SAMPLE_BRANCH_STACK feature
    > of perf_events.
    >
    > There is a new option to active this mode: -b.
    > It is possible to pass a set of filters to select the type of
    > branches to sample.
    >
    > The following filters are available:
    > - any : any type of branches
    > - any_call : any function call or system call
    > - any_ret : any function return or system call return
    > - any_ind : any indirect branch
    > - u: only when the branch target is at the user level
    > - k: only when the branch target is in the kernel
    > - hv: only when the branch target is in the hypervisor
    >
    > Filters can be combined by passing a comma separated list
    > to the option:
    >
    > $ perf record -b any_call,u -e cycles:u branchy
    >
    > Signed-off-by: Roberto Agostino Vitillo <ravitillo@lbl.gov>
    > Signed-off-by: Stephane Eranian <eranian@google.com>
    > ---
    > tools/perf/Documentation/perf-record.txt | 25 ++++++++++
    > tools/perf/builtin-record.c | 74 ++++++++++++++++++++++++++++++
    > tools/perf/perf.h | 1 +
    > tools/perf/util/evsel.c | 4 ++
    > 4 files changed, 104 insertions(+), 0 deletions(-)
    >
    > diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
    > index ff9a66e..288d429 100644
    > --- a/tools/perf/Documentation/perf-record.txt
    > +++ b/tools/perf/Documentation/perf-record.txt
    > @@ -152,6 +152,31 @@ an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must ha
    > corresponding events, i.e., they always refer to events defined earlier on the command
    > line.
    >
    > +-b::
    > +--branch-stack::
    > +Enable taken branch stack sampling. Each sample captures a series of consecutive
    > +taken branches. The number of branches captured with each sample depends on the
    > +underlying hardware, the type of branches of interest, and the executed code.
    > +It is possible to select the types of branches captured by enabling filters. The
    > +following filters are defined:
    > +
    > + - any : any type of branches
    > + - any_call: any function call or system call
    > + - any_ret: any function return or system call return
    > + - any_ind: any indirect branch
    > + - u: only when the branch target is at the user level
    > + - k: only when the branch target is in the kernel
    > + - hv: only when the target is at the hypervisor level
    > +
    > ++
    > +At least one of any, any_call, any_ret, any_ind must be provided. The privilege levels may
    > +be ommitted, in which case, the privilege levels of the associated event are applied to the
    > +branch filter. Both kernel (k) and hypervisor (hv) privilege levels are subject to
    > +permissions. When sampling on multiple events, branch stack sampling is enabled for all
    > +the sampling events. The sampled branch type is the same for all events.
    > +Note that taken branch sampling may not be available on all processors.
    > +The various filters must be specified as a comma separated list: -b any_ret,u,k
    > +
    > SEE ALSO
    > --------
    > linkperf:perf-stat[1], linkperf:perf-list[1]
    > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
    > index 32870ee..7df6e68 100644
    > --- a/tools/perf/builtin-record.c
    > +++ b/tools/perf/builtin-record.c
    > @@ -637,6 +637,77 @@ static int __cmd_record(struct perf_record *rec, int argc, const char **argv)
    > return err;
    > }
    >
    > +#define BRANCH_OPT(n, m) \
    > + { .name = n, .mode = (m) }
    > +
    > +#define BRANCH_END { .name = NULL }
    > +
    > +struct branch_mode {
    > + const char *name;
    > + int mode;
    > +};
    > +
    > +static const struct branch_mode branch_modes[] = {
    > + BRANCH_OPT("u", PERF_SAMPLE_BRANCH_USER),
    > + BRANCH_OPT("k", PERF_SAMPLE_BRANCH_KERNEL),
    > + BRANCH_OPT("hv", PERF_SAMPLE_BRANCH_HV),
    > + BRANCH_OPT("any", PERF_SAMPLE_BRANCH_ANY),
    > + BRANCH_OPT("any_call", PERF_SAMPLE_BRANCH_ANY_CALL),
    > + BRANCH_OPT("any_ret", PERF_SAMPLE_BRANCH_ANY_RETURN),
    > + BRANCH_OPT("ind_call", PERF_SAMPLE_BRANCH_IND_CALL),
    > + BRANCH_END
    > +};
    > +
    > +static int
    > +parse_branch_stack(const struct option *opt, const char *str, int unset __used)
    > +{
    > +#define ONLY_PLM \
    > + (PERF_SAMPLE_BRANCH_USER |\
    > + PERF_SAMPLE_BRANCH_KERNEL |\
    > + PERF_SAMPLE_BRANCH_KERNEL)

    I guess this would be PERF_SAMPLE_BRANCH_HV instead of the second
    PERF_SAMPLE_BRANCH_KERNEL.

    > +
    > + uint64_t *mode = (uint64_t *)opt->value;
    > + const struct branch_mode *br;
    > + char *s, *os, *p;
    > + int ret = -1;
    > +
    > + *mode = 0;
    > +
    > + /* because str is read-only */
    > + s = os = strdup(str);
    > + if (!s)
    > + return -1;
    > +
    > + for (;;) {
    > + p = strchr(s, ',');
    > + if (p)
    > + *p = '\0';
    > +
    > + for (br = branch_modes; br->name; br++) {
    > + if (!strcasecmp(s, br->name))
    > + break;
    > + }
    > + if (!br->name)
    > + goto error;
    > +
    > + *mode |= br->mode;
    > +
    > + if (!p)
    > + break;
    > +
    > + s = p + 1;
    > + }
    > + ret = 0;
    > +
    > + if ((*mode & ~ONLY_PLM) == 0) {
    > + error("need at least one branch type with -b\n");
    > + ret = -1;
    > + }
    > +error:
    > + free(os);
    > + return ret;
    > +}
    > +
    > static const char * const record_usage[] = {
    > "perf record [<options>] [<command>]",
    > "perf record [<options>] -- <command> [<options>]",
    > @@ -729,6 +800,9 @@ const struct option record_options[] = {
    > "monitor event in cgroup name only",
    > parse_cgroups),
    > OPT_STRING('u', "uid", &record.uid_str, "user", "user to profile"),
    > + OPT_CALLBACK('b', "branch-stack", &record.opts.branch_stack,
    > + "branch mode mask", "branch stack sampling modes",
    > + parse_branch_stack),
    > OPT_END()
    > };
    >
    > diff --git a/tools/perf/perf.h b/tools/perf/perf.h
    > index 8b4d25d..7f8fbab 100644
    > --- a/tools/perf/perf.h
    > +++ b/tools/perf/perf.h
    > @@ -222,6 +222,7 @@ struct perf_record_opts {
    > unsigned int freq;
    > unsigned int mmap_pages;
    > unsigned int user_freq;
    > + int branch_stack;
    > u64 default_interval;
    > u64 user_interval;
    > const char *cpu_list;
    > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
    > index 472fc8c..a65a53c 100644
    > --- a/tools/perf/util/evsel.c
    > +++ b/tools/perf/util/evsel.c
    > @@ -126,6 +126,10 @@ void perf_evsel__config(struct perf_evsel *evsel, struct perf_record_opts *opts)
    > attr->watermark = 0;
    > attr->wakeup_events = 1;
    > }
    > + if (opts->branch_stack) {
    > + attr->sample_type |= PERF_SAMPLE_BRANCH_STACK;
    > + attr->branch_sample_type = opts->branch_stack;
    > + }
    >
    > attr->mmap = track;
    > attr->comm = track;


    --
    Anshuman Khandual
    Linux Technology Centre
    IBM Systems and Technology Group



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