4 files changed, 112 insertions, 2 deletions

diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt
index 6ce95858cd4e..8fff0618c597 100644
--- a/tools/perf/Documentation/perf-diff.txt
+++ b/tools/perf/Documentation/perf-diff.txt
@@ -76,6 +76,39 @@ OPTIONS
 --baseline-only::
         Show only items with match in baseline.
 
+-c::
+--compute::
+        Differential computation selection - delta,ratio (default is delta).
+        See COMPARISON METHODS section for more info.
+
+COMPARISON METHODS
+------------------
+delta
+~~~~~
+If specified the 'Delta' column is displayed with value 'd' computed as:
+
+  d = A->period_percent - B->period_percent
+
+with:
+  - A/B being matching hist entry from first/second file specified
+    (or perf.data/perf.data.old) respectively.
+
+  - period_percent being the % of the hist entry period value within
+    single data file
+
+ratio
+~~~~~
+If specified the 'Ratio' column is displayed with value 'r' computed as:
+
+  r = A->period / B->period
+
+with:
+  - A/B being matching hist entry from first/second file specified
+    (or perf.data/perf.data.old) respectively.
+
+  - period being the hist entry period value
+
+
 SEE ALSO
 --------
 linkperf:perf-record[1]
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 1063c31e507c..e90c06aea4d4 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -26,6 +26,41 @@ static bool  force;
 static bool show_displacement;
 static bool show_baseline_only;
 
+enum {
+        COMPUTE_DELTA,
+        COMPUTE_RATIO,
+        COMPUTE_MAX,
+};
+
+const char *compute_names[COMPUTE_MAX] = {
+        [COMPUTE_DELTA] = "delta",
+        [COMPUTE_RATIO] = "ratio",
+};
+
+static int compute;
+
+static int setup_compute(const struct option *opt, const char *str,
+                         int unset __maybe_unused)
+{
+        int *cp = (int *) opt->value;
+        unsigned i;
+
+        if (!str) {
+                *cp = COMPUTE_DELTA;
+                return 0;
+        }
+
+        for (i = 0; i < COMPUTE_MAX; i++)
+                if (!strcmp(str, compute_names[i])) {
+                        *cp = i;
+                        return 0;
+                }
+
+        pr_err("Failed: '%s' is not computation method "
+               "(use 'delta' or 'ratio').\n", str);
+        return -EINVAL;
+}
+
 static int hists__add_entry(struct hists *self,
                             struct addr_location *al, u64 period)
 {
@@ -262,6 +297,9 @@ static const struct option options[] = {
                     "Show position displacement relative to baseline"),
         OPT_BOOLEAN('b', "baseline-only", &show_baseline_only,
                     "Show only items with match in baseline"),
+        OPT_CALLBACK('c', "compute", &compute, "delta,ratio (default delta)",
+                     "Entries differential computation selection",
+                     setup_compute),
         OPT_BOOLEAN('D', "dump-raw-trace", &dump_trace,
                     "dump raw trace in ASCII"),
         OPT_BOOLEAN('f', "force", &force, "don't complain, do it"),
@@ -290,9 +328,19 @@ static void ui_init(void)
         /* No overhead column. */
         perf_hpp__column_enable(PERF_HPP__OVERHEAD, false);
 
-        /* Display baseline/delta/displacement columns. */
+        /* Display baseline/delta/ratio/displacement columns. */
         perf_hpp__column_enable(PERF_HPP__BASELINE, true);
-        perf_hpp__column_enable(PERF_HPP__DELTA, true);
+
+        switch (compute) {
+        case COMPUTE_DELTA:
+                perf_hpp__column_enable(PERF_HPP__DELTA, true);
+                break;
+        case COMPUTE_RATIO:
+                perf_hpp__column_enable(PERF_HPP__RATIO, true);
+                break;
+        default:
+                BUG_ON(1);
+        };
 
         if (show_displacement)
                 perf_hpp__column_enable(PERF_HPP__DISPL, true);
diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
index f5a1e4f65263..1b633a4b5c45 100644
--- a/tools/perf/ui/hist.c
+++ b/tools/perf/ui/hist.c
@@ -266,6 +266,33 @@ static int hpp__entry_delta(struct perf_hpp *hpp, struct hist_entry *he)
         return scnprintf(hpp->buf, hpp->size, fmt, buf);
 }
 
+static int hpp__header_ratio(struct perf_hpp *hpp)
+{
+        const char *fmt = symbol_conf.field_sep ? "%s" : "%14s";
+
+        return scnprintf(hpp->buf, hpp->size, fmt, "Ratio");
+}
+
+static int hpp__width_ratio(struct perf_hpp *hpp __maybe_unused)
+{
+        return 14;
+}
+
+static int hpp__entry_ratio(struct perf_hpp *hpp, struct hist_entry *he)
+{
+        struct hist_entry *pair = he->pair;
+        double new_period = he->stat.period;
+        double old_period = pair ? pair->stat.period : 0;
+        double ratio = pair ? new_period / old_period : 0;
+        const char *fmt = symbol_conf.field_sep ? "%s" : "%14s";
+        char buf[32] = " ";
+
+        if (ratio > 0.0)
+                scnprintf(buf, sizeof(buf), "%+14.6F", ratio);
+
+        return scnprintf(hpp->buf, hpp->size, fmt, buf);
+}
+
 static int hpp__header_displ(struct perf_hpp *hpp)
 {
         return scnprintf(hpp->buf, hpp->size, "Displ.");
@@ -311,6 +338,7 @@ struct perf_hpp_fmt perf_hpp__format[] = {
         { .cond = false, HPP__PRINT_FNS(samples) },
         { .cond = false, HPP__PRINT_FNS(period) },
         { .cond = false, HPP__PRINT_FNS(delta) },
+        { .cond = false, HPP__PRINT_FNS(ratio) },
         { .cond = false, HPP__PRINT_FNS(displ) }
 };
 
diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index 66cb31fe81d2..7e4d4c262213 100644
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -141,6 +141,7 @@ enum {
         PERF_HPP__SAMPLES,
         PERF_HPP__PERIOD,
         PERF_HPP__DELTA,
+        PERF_HPP__RATIO,
         PERF_HPP__DISPL,
 
         PERF_HPP__MAX_INDEX