lkml.org 
[lkml]   [2011]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 11/12] perf: add support for sampling taken branch to perf record
Date
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

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 | 18 +++++++
tools/perf/builtin-record.c | 75 ++++++++++++++++++++++++++++++
2 files changed, 93 insertions(+), 0 deletions(-)
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5a520f8..ddc1999 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -148,6 +148,24 @@ 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 interested and the executed code.
+It is possible to filter the types of branches 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). 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 is applied to the branch filter. 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. The privilege levels are adjusted based on those of
+the associated event unless specified explicitly with this option. 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 f4c3fbe..4464677 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -57,6 +57,7 @@ static pid_t child_pid = -1;
static bool no_inherit = false;
static enum write_mode_t write_mode = WRITE_FORCE;
static bool call_graph = false;
+static int branch_stack = 0;
static bool inherit_stat = false;
static bool no_samples = false;
static bool sample_address = false;
@@ -204,6 +205,11 @@ static void config_attr(struct perf_evsel *evsel, struct perf_evlist *evlist)
if (system_wide)
attr->sample_type |= PERF_SAMPLE_CPU;

+ if (branch_stack) {
+ attr->sample_type |= PERF_SAMPLE_BRANCH_STACK;
+ attr->branch_sample_type = branch_stack;
+ }
+
if (sample_id_all_avail &&
(sample_time || system_wide || !no_inherit || cpu_list))
attr->sample_type |= PERF_SAMPLE_TIME;
@@ -717,6 +723,72 @@ out_delete_session:
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("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)
+ 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) {
+ pr_warning("error: needs 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>]",
@@ -777,6 +849,9 @@ const struct option record_options[] = {
OPT_CALLBACK('G', "cgroup", &evsel_list, "name",
"monitor event in cgroup name only",
parse_cgroups),
+ OPT_CALLBACK('b', "branch stack", &branch_stack, "branch mode mask",
+ "branch stack sampling modes",
+ parse_branch_stack),
OPT_END()
};

--
1.7.4.1


\
 
 \ /
  Last update: 2011-10-06 16:53    [from the cache]
©2003-2011 Jasper Spaans