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perf tools: Enable LBR call stack support

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Currently, there are two call chain recording options, fp and dwarf.

Haswell has a new feature that utilizes the existing LBR facility to
record call chains. Kernel side LBR support code provides this as a
third option to record call chains. This patch enables the lbr call
stack support on the tooling side.

LBR call stack has some limitations:

 - It reuses current LBR facility, so LBR call stack and branch record
   can not be enabled at the same time.

 - It is only available for user-space callchains.

However, it also offers some advantages:

 - LBR call stack can work on user apps which don't have frame-pointers
   or dwarf debug info compiled. It is a good alternative when nothing
   else works.

Tested-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Jacob Shin <jacob.w.shin@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masanari Iida <standby24x7@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rodrigo Campos <rodrigo@sdfg.com.ar>
Cc: Stephane Eranian <eranian@google.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1420482185-29830-2-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kan Liang 2015-01-05 13:23:04 -05:00 committed by Ingo Molnar
parent 2c44b1936b
commit aad2b21c15
6 changed files with 40 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
tools/perf/Documentation/perf-record.txt
View File

@ -115,13 +115,19 @@ OPTIONS
implies -g.
Allows specifying "fp" (frame pointer) or "dwarf"
(DWARF's CFI - Call Frame Information) as the method to collect
(DWARF's CFI - Call Frame Information) or "lbr"
(Hardware Last Branch Record facility) as the method to collect
the information used to show the call graphs.
In some systems, where binaries are build with gcc
--fomit-frame-pointer, using the "fp" method will produce bogus
call graphs, using "dwarf", if available (perf tools linked to
the libunwind library) should be used instead.
Using the "lbr" method doesn't require any compiler options. It
will produce call graphs from the hardware LBR registers. The
main limition is that it is only available on new Intel
platforms, such as Haswell. It can only get user call chain. It
doesn't work with branch stack sampling at the same time.
-q::
--quiet::

6
tools/perf/builtin-record.c
View File

@ -658,7 +658,7 @@ error:
static void callchain_debug(void)
{
static const char *str[CALLCHAIN_MAX] = { "NONE", "FP", "DWARF" };
static const char *str[CALLCHAIN_MAX] = { "NONE", "FP", "DWARF", "LBR" };
pr_debug("callchain: type %s\n", str[callchain_param.record_mode]);
@ -751,9 +751,9 @@ static struct record record = {
#define CALLCHAIN_HELP "setup and enables call-graph (stack chain/backtrace) recording: "
#ifdef HAVE_DWARF_UNWIND_SUPPORT
const char record_callchain_help[] = CALLCHAIN_HELP "fp dwarf";
const char record_callchain_help[] = CALLCHAIN_HELP "fp dwarf lbr";
#else
const char record_callchain_help[] = CALLCHAIN_HELP "fp";
const char record_callchain_help[] = CALLCHAIN_HELP "fp lbr";
#endif
/*

2
tools/perf/builtin-report.c
View File

@ -249,6 +249,8 @@ static int report__setup_sample_type(struct report *rep)
if ((sample_type & PERF_SAMPLE_REGS_USER) &&
(sample_type & PERF_SAMPLE_STACK_USER))
callchain_param.record_mode = CALLCHAIN_DWARF;
else if (sample_type & PERF_SAMPLE_BRANCH_STACK)
callchain_param.record_mode = CALLCHAIN_LBR;
else
callchain_param.record_mode = CALLCHAIN_FP;
}

8
tools/perf/util/callchain.c
View File

@ -97,6 +97,14 @@ int parse_callchain_record_opt(const char *arg)
callchain_param.dump_size = size;
}
#endif /* HAVE_DWARF_UNWIND_SUPPORT */
} else if (!strncmp(name, "lbr", sizeof("lbr"))) {
if (!strtok_r(NULL, ",", &saveptr)) {
callchain_param.record_mode = CALLCHAIN_LBR;
ret = 0;
} else
pr_err("callchain: No more arguments "
"needed for --call-graph lbr\n");
break;
} else {
pr_err("callchain: Unknown --call-graph option "
"value: %s\n", arg);

1
tools/perf/util/callchain.h
View File

@ -11,6 +11,7 @@ enum perf_call_graph_mode {
CALLCHAIN_NONE,
CALLCHAIN_FP,
CALLCHAIN_DWARF,
CALLCHAIN_LBR,
CALLCHAIN_MAX
};

21
tools/perf/util/evsel.c
View File

@ -537,13 +537,30 @@ int perf_evsel__group_desc(struct perf_evsel *evsel, char *buf, size_t size)
}
static void
perf_evsel__config_callgraph(struct perf_evsel *evsel)
perf_evsel__config_callgraph(struct perf_evsel *evsel,
struct record_opts *opts)
{
bool function = perf_evsel__is_function_event(evsel);
struct perf_event_attr *attr = &evsel->attr;
perf_evsel__set_sample_bit(evsel, CALLCHAIN);
if (callchain_param.record_mode == CALLCHAIN_LBR) {
if (!opts->branch_stack) {
if (attr->exclude_user) {
pr_warning("LBR callstack option is only available "
"to get user callchain information. "
"Falling back to framepointers.\n");
} else {
perf_evsel__set_sample_bit(evsel, BRANCH_STACK);
attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER |
PERF_SAMPLE_BRANCH_CALL_STACK;
}
} else
pr_warning("Cannot use LBR callstack with branch stack. "
"Falling back to framepointers.\n");
}
if (callchain_param.record_mode == CALLCHAIN_DWARF) {
if (!function) {
perf_evsel__set_sample_bit(evsel, REGS_USER);
@ -667,7 +684,7 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts)
evsel->attr.exclude_callchain_user = 1;
if (callchain_param.enabled && !evsel->no_aux_samples)
perf_evsel__config_callgraph(evsel);
perf_evsel__config_callgraph(evsel, opts);
if (opts->sample_intr_regs) {
attr->sample_regs_intr = PERF_REGS_MASK;