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authorKan Liang <kan.liang@linux.intel.com>2020-03-19 23:25:15 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2020-04-18 15:05:01 +0300
commit13e0c844fa097f657bd8204fd574477c34f47a0c (patch)
tree4f6f4d1c0b86b211267dcfa80e99e91b87b60749 /tools
parent680d125cd522d460b24ccc8b29f03cdb62dea23e (diff)
downloadlinux-13e0c844fa097f657bd8204fd574477c34f47a0c.tar.xz
perf top: Add option to enable the LBR stitching approach
With the LBR stitching approach, the reconstructed LBR call stack can break the HW limitation. However, it may reconstruct invalid call stacks in some cases, e.g. exception handing such as setjmp/longjmp. Also, it may impact the processing time especially when the number of samples with stitched LBRs are huge. Add an option to enable the approach. The option must be used with --call-graph lbr. Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Acked-by: Jiri Olsa <jolsa@redhat.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexey Budankov <alexey.budankov@linux.intel.com> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Pavel Gerasimov <pavel.gerasimov@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com> Cc: Stephane Eranian <eranian@google.com> Cc: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com> Link: http://lore.kernel.org/lkml/20200319202517.23423-16-kan.liang@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/Documentation/perf-top.txt9
-rw-r--r--tools/perf/builtin-top.c11
-rw-r--r--tools/perf/util/top.h1
3 files changed, 21 insertions, 0 deletions
diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 487737a725e9..20227dabc208 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -319,6 +319,15 @@ Default is to monitor all CPUS.
go straight to the histogram browser, just like 'perf top' with no events
explicitely specified does.
+--stitch-lbr::
+ Show callgraph with stitched LBRs, which may have more complete
+ callgraph. The option must be used with --call-graph lbr recording.
+ Disabled by default. In common cases with call stack overflows,
+ it can recreate better call stacks than the default lbr call stack
+ output. But this approach is not full proof. There can be cases
+ where it creates incorrect call stacks from incorrect matches.
+ The known limitations include exception handing such as
+ setjmp/longjmp will have calls/returns not match.
INTERACTIVE PROMPTING KEYS
--------------------------
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 289cf83e658a..6b067a5ba1d5 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -33,6 +33,7 @@
#include "util/map.h"
#include "util/mmap.h"
#include "util/session.h"
+#include "util/thread.h"
#include "util/symbol.h"
#include "util/synthetic-events.h"
#include "util/top.h"
@@ -775,6 +776,9 @@ static void perf_event__process_sample(struct perf_tool *tool,
if (machine__resolve(machine, &al, sample) < 0)
return;
+ if (top->stitch_lbr)
+ al.thread->lbr_stitch_enable = true;
+
if (!machine->kptr_restrict_warned &&
symbol_conf.kptr_restrict &&
al.cpumode == PERF_RECORD_MISC_KERNEL) {
@@ -1571,6 +1575,8 @@ int cmd_top(int argc, const char **argv)
"Sort the output by the event at the index n in group. "
"If n is invalid, sort by the first event. "
"WARNING: should be used on grouped events."),
+ OPT_BOOLEAN(0, "stitch-lbr", &top.stitch_lbr,
+ "Enable LBR callgraph stitching approach"),
OPTS_EVSWITCH(&top.evswitch),
OPT_END()
};
@@ -1640,6 +1646,11 @@ int cmd_top(int argc, const char **argv)
}
}
+ if (top.stitch_lbr && !(callchain_param.record_mode == CALLCHAIN_LBR)) {
+ pr_err("Error: --stitch-lbr must be used with --call-graph lbr\n");
+ goto out_delete_evlist;
+ }
+
if (opts->branch_stack && callchain_param.enabled)
symbol_conf.show_branchflag_count = true;
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index f117d4f4821e..45dc84ddff37 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -36,6 +36,7 @@ struct perf_top {
bool use_tui, use_stdio;
bool vmlinux_warned;
bool dump_symtab;
+ bool stitch_lbr;
struct hist_entry *sym_filter_entry;
struct evsel *sym_evsel;
struct perf_session *session;