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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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