perf diff: Support --cpu filter option

To improve 'perf diff', implement a --cpu filter option.

Multiple CPUs can be provided as a comma-separated list with no space:
0,1.  Ranges of CPUs are specified with -: 0-2. Default is to report
samples on all CPUs.

For example,

  perf diff --cpu 0,1

It only diff the samples for CPU0 and CPU1.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1551791143-10334-3-git-send-email-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 21 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt
index 036d65bded51..8c2c229faf50 100644
--- a/tools/perf/Documentation/perf-diff.txt
+++ b/tools/perf/Documentation/perf-diff.txt
@@ -163,6 +163,11 @@ OPTIONS
         the end of perf.data.old and analyzes the perf.data from the
         timestamp 3971.150589 to the end of perf.data.
 
+--cpu:: Only diff samples for the list of CPUs provided. Multiple CPUs can
+        be provided as a comma-separated list with no space: 0,1. Ranges of
+        CPUs are specified with -: 0-2. Default is to report samples on all
+        CPUs.
+
 COMPARISON
 ----------
 The comparison is governed by the baseline file. The baseline perf.data
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 17cd898074c8..dfe6c7606f5a 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -83,6 +83,9 @@ static unsigned int sort_compute = 1;
 static s64 compute_wdiff_w1;
 static s64 compute_wdiff_w2;
 
+static const char               *cpu_list;
+static DECLARE_BITMAP(cpu_bitmap, MAX_NR_CPUS);
+
 enum {
         COMPUTE_DELTA,
         COMPUTE_RATIO,
@@ -354,6 +357,11 @@ static int diff__process_sample_event(struct perf_tool *tool,
                 return -1;
         }
 
+        if (cpu_list && !test_bit(sample->cpu, cpu_bitmap)) {
+                ret = 0;
+                goto out_put;
+        }
+
         if (!hists__add_entry(hists, &al, NULL, NULL, NULL, sample, true)) {
                 pr_warning("problem incrementing symbol period, skipping event\n");
                 goto out_put;
@@ -892,6 +900,13 @@ static int __cmd_diff(void)
                                 goto out_delete;
                 }
 
+                if (cpu_list) {
+                        ret = perf_session__cpu_bitmap(d->session, cpu_list,
+                                                       cpu_bitmap);
+                        if (ret < 0)
+                                goto out_delete;
+                }
+
                 ret = perf_session__process_events(d->session);
                 if (ret) {
                         pr_err("Failed to process %s\n", d->data.path);
@@ -969,6 +984,7 @@ static const struct option options[] = {
                      "How to display percentage of filtered entries", parse_filter_percentage),
         OPT_STRING(0, "time", &pdiff.time_str, "str",
                    "Time span (time percent or absolute timestamp)"),
+        OPT_STRING(0, "cpu", &cpu_list, "cpu", "list of cpus to profile"),
         OPT_END()
 };