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Date: Thu, 16 May 2024 15:21:59 -0700
Message-Id: <20240516222159.3710131-1-irogers@google.com>
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Subject: [PATCH v1] perf top: Make zeroing histogram on refresh the default
From: Ian Rogers <irogers@google.com>
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Namhyung Kim <namhyung@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	Ian Rogers <irogers@google.com>, Adrian Hunter <adrian.hunter@intel.com>, 
	Kan Liang <kan.liang@linux.intel.com>, Changbin Du <changbin.du@huawei.com>, 
	John Fastabend <john.fastabend@gmail.com>, Andrii Nakryiko <andrii@kernel.org>, 
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, 
	Stephane Eranian <eranian@google.com>
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Instead of decaying histograms over time change it so that they are
zero-ed on each perf top refresh. Previously the option '-z', or
pressing 'z' in tui mode, would enable this behavior. Decaying samples
is non-intuitive as it isn't how "top" works. Make zeroing on refresh
the default and rename the command line options from 'z' to 'Z' and
'zero' to 'decay'.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/Documentation/perf-top.txt |  6 +++---
 tools/perf/builtin-top.c              | 23 +++++++++++++----------
 tools/perf/ui/browsers/hists.c        |  7 ++++---
 tools/perf/util/top.h                 |  2 +-
 4 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 667e5102075e..f1524cc0d409 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -124,9 +124,9 @@ Default is to monitor all CPUS.
 --verbose::
 	Be more verbose (show counter open errors, etc).
 
--z::
---zero::
-	Zero history across display updates.
+-Z::
+--decay::
+	Decay rather than zero history across display updates.
 
 -s::
 --sort::
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index e8cbbf10d361..8f06635cb7cd 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -266,10 +266,10 @@ static void perf_top__show_details(struct perf_top *top)
 	more = symbol__annotate_printf(&he->ms, top->sym_evsel);
 
 	if (top->evlist->enabled) {
-		if (top->zero)
-			symbol__annotate_zero_histogram(symbol, top->sym_evsel->core.idx);
-		else
+		if (top->decay_samples)
 			symbol__annotate_decay_histogram(symbol, top->sym_evsel->core.idx);
+		else
+			symbol__annotate_zero_histogram(symbol, top->sym_evsel->core.idx);
 	}
 	if (more != 0)
 		printf("%d lines not displayed, maybe increase display entries [e]\n", more);
@@ -292,11 +292,11 @@ static void perf_top__resort_hists(struct perf_top *t)
 		hists__unlink(hists);
 
 		if (evlist->enabled) {
-			if (t->zero) {
-				hists__delete_entries(hists);
-			} else {
+			if (t->decay_samples) {
 				hists__decay_entries(hists, t->hide_user_symbols,
 						     t->hide_kernel_symbols);
+			} else {
+				hists__delete_entries(hists);
 			}
 		}
 
@@ -460,7 +460,9 @@ static void perf_top__print_mapped_keys(struct perf_top *top)
 	fprintf(stdout,
 		"\t[U]     hide user symbols.               \t(%s)\n",
 		top->hide_user_symbols ? "yes" : "no");
-	fprintf(stdout, "\t[z]     toggle sample zeroing.             \t(%d)\n", top->zero ? 1 : 0);
+	fprintf(stdout,
+		"\t[z]     toggle sample zeroing/decaying.  \t(%s)\n",
+		top->decay_samples ? "decay" : "zero");
 	fprintf(stdout, "\t[qQ]    quit.\n");
 }
 
@@ -583,7 +585,7 @@ static bool perf_top__handle_keypress(struct perf_top *top, int c)
 			top->hide_user_symbols = !top->hide_user_symbols;
 			break;
 		case 'z':
-			top->zero = !top->zero;
+			top->decay_samples = !top->decay_samples;
 			break;
 		default:
 			break;
@@ -648,7 +650,7 @@ static void *display_thread_tui(void *arg)
 	ret = evlist__tui_browse_hists(top->evlist, help, &hbt, top->min_percent,
 				       &top->session->header.env, !top->record_opts.overwrite);
 	if (ret == K_RELOAD) {
-		top->zero = true;
+		top->decay_samples = false;
 		goto repeat;
 	} else
 		stop_top();
@@ -1502,7 +1504,8 @@ int cmd_top(int argc, const char **argv)
 		    "child tasks do not inherit counters"),
 	OPT_STRING(0, "sym-annotate", &top.sym_filter, "symbol name",
 		    "symbol to annotate"),
-	OPT_BOOLEAN('z', "zero", &top.zero, "zero history across updates"),
+	OPT_BOOLEAN('Z', "decay", &top.decay_samples,
+		    "decay rather than zero history across updates"),
 	OPT_CALLBACK('F', "freq", &top.record_opts, "freq or 'max'",
 		     "profile at this frequency",
 		      record__parse_freq),
diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index b7219df51236..bcc4720f8198 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -2305,8 +2305,8 @@ static int hists_browser__scnprintf_title(struct hist_browser *browser, char *bf
 				     " drop: %" PRIu64 "/%" PRIu64,
 				     top->drop, top->drop_total);
 
-		if (top->zero)
-			printed += scnprintf(bf + printed, size - printed, " [z]");
+		if (top->decay_samples)
+			printed += scnprintf(bf + printed, size - printed, " [decay]");
 
 		perf_top__reset_sample_counters(top);
 	}
@@ -3209,9 +3209,10 @@ static int evsel__hists_browse(struct evsel *evsel, int nr_events, const char *h
 			continue;
 		case 'z':
 			if (!is_report_browser(hbt)) {
+				/* Toggle between zeroing and decaying samples. */
 				struct perf_top *top = hbt->arg;
 
-				top->zero = !top->zero;
+				top->decay_samples = !top->decay_samples;
 			}
 			continue;
 		case 'L':
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index 4c5588dbb131..b2c199925b36 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -32,7 +32,7 @@ struct perf_top {
 	u64		   guest_us_samples, guest_kernel_samples;
 	int		   print_entries, count_filter, delay_secs;
 	int		   max_stack;
-	bool		   hide_kernel_symbols, hide_user_symbols, zero;
+	bool		   hide_kernel_symbols, hide_user_symbols, decay_samples;
 #ifdef HAVE_SLANG_SUPPORT
 	bool		   use_tui;
 #endif
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog