perf report: Implement browsing of individual samples

Now 'perf report' can show whole time periods with 'perf script', but
the user still has to find individual samples of interest manually.

It would be expensive and complicated to search for the right samples in
the whole perf file. Typically users only need to look at a small number
of samples for useful analysis.

Also the full scripts tend to show samples of all CPUs and all threads
mixed up, which can be very confusing on larger systems.

Add a new --samples option to save a small random number of samples per
hist entry.

Use a reservoir sample technique to select a representatve number of
samples.

Then allow browsing the samples using 'perf script' as part of the hist
entry context menu. This automatically adds the right filters, so only
the thread or cpu of the sample is displayed. Then we use less' search
functionality to directly jump the to the time stamp of the selected
sample.

It uses different menus for assembler and source display. Assembler
needs xed installed and source needs debuginfo.

Currently it only supports as many samples as fit on the screen due to
some limitations in the slang ui code.

Signed-off-by: Andi Kleen <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-config.txt

···
 	llvm.opts::
 		Options passed to llc.
 
+samples.*::
+
+	samples.context::
+		Define how many ns worth of time to show
+		around samples in perf report sample context browser.
+
 SEE ALSO
 --------
 linkperf:perf[1]

tools/perf/Documentation/perf-report.txt

···
 --socket-filter::
 	Only report the samples on the processor socket that match with this filter
 
+--samples=N::
+	Save N individual samples for each histogram entry to show context in perf
+	report tui browser.
+
 --raw-trace::
 	When displaying traceevent output, do not use print fmt or plugins.
 

tools/perf/builtin-report.c

···
 	OPT_BOOLEAN(0, "demangle-kernel", &symbol_conf.demangle_kernel,
 		    "Enable kernel symbol demangling"),
 	OPT_BOOLEAN(0, "mem-mode", &report.mem_mode, "mem access profile"),
+	OPT_INTEGER(0, "samples", &symbol_conf.res_sample,
+		    "Number of samples to save per histogram entry for individual browsing"),
 	OPT_CALLBACK(0, "percent-limit", &report, "percent",
 		     "Don't show entries under that percent", parse_percent_limit),
 	OPT_CALLBACK(0, "percentage", NULL, "relative|absolute",

tools/perf/ui/browsers/Build

···
 perf-y += map.o
 perf-y += scripts.o
 perf-y += header.o
+perf-y += res_sample.o
 
 CFLAGS_annotate.o += -DENABLE_SLFUTURE_CONST
 CFLAGS_hists.o    += -DENABLE_SLFUTURE_CONST

tools/perf/ui/browsers/hists.c

···
 				hist_browser__hpp_color_overhead_guest_us;
 	perf_hpp__format[PERF_HPP__OVERHEAD_ACC].color =
 				hist_browser__hpp_color_overhead_acc;
+
+	res_sample_init();
 }
 
 static int hist_browser__show_entry(struct hist_browser *browser,
···
 	struct map_symbol 	ms;
 	int			socket;
 	struct perf_evsel	*evsel;
+	enum rstype		rstype;
 
 	int (*fn)(struct hist_browser *browser, struct popup_action *act);
 };
···
 }
 
 static int
+do_res_sample_script(struct hist_browser *browser __maybe_unused,
+		     struct popup_action *act)
+{
+	struct hist_entry *he;
+
+	he = hist_browser__selected_entry(browser);
+	res_sample_browse(he->res_samples, he->num_res, act->evsel, act->rstype);
+	return 0;
+}
+
+static int
 add_script_opt_2(struct hist_browser *browser __maybe_unused,
 	       struct popup_action *act, char **optstr,
 	       struct thread *thread, struct symbol *sym,
···
 		act->time = he->time;
 	}
 	return n;
+}
+
+static int
+add_res_sample_opt(struct hist_browser *browser __maybe_unused,
+		   struct popup_action *act, char **optstr,
+		   struct res_sample *res_sample,
+		   struct perf_evsel *evsel,
+		   enum rstype type)
+{
+	if (!res_sample)
+		return 0;
+
+	if (asprintf(optstr, "Show context for individual samples %s",
+		type == A_ASM ? "with assembler" :
+		type == A_SOURCE ? "with source" : "") < 0)
+		return 0;
+
+	act->fn = do_res_sample_script;
+	act->evsel = evsel;
+	act->rstype = type;
+	return 1;
 }
 
 static int
···
 		}
 		nr_options += add_script_opt(browser, &actions[nr_options],
 					     &options[nr_options], NULL, NULL, evsel);
+		nr_options += add_res_sample_opt(browser, &actions[nr_options],
+						 &options[nr_options],
+				 hist_browser__selected_entry(browser)->res_samples,
+				 evsel, A_NORMAL);
+		nr_options += add_res_sample_opt(browser, &actions[nr_options],
+						 &options[nr_options],
+				 hist_browser__selected_entry(browser)->res_samples,
+				 evsel, A_ASM);
+		nr_options += add_res_sample_opt(browser, &actions[nr_options],
+						 &options[nr_options],
+				 hist_browser__selected_entry(browser)->res_samples,
+				 evsel, A_SOURCE);
 		nr_options += add_switch_opt(browser, &actions[nr_options],
 					     &options[nr_options]);
 skip_scripting:

tools/perf/ui/browsers/res_sample.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Display a menu with individual samples to browse with perf script */
+#include "util.h"
+#include "hist.h"
+#include "evsel.h"
+#include "hists.h"
+#include "sort.h"
+#include "config.h"
+#include "time-utils.h"
+#include <linux/time64.h>
+
+static u64 context_len = 10 * NSEC_PER_MSEC;
+
+static int res_sample_config(const char *var, const char *value, void *data __maybe_unused)
+{
+	if (!strcmp(var, "samples.context"))
+		return perf_config_u64(&context_len, var, value);
+	return 0;
+}
+
+void res_sample_init(void)
+{
+	perf_config(res_sample_config, NULL);
+}
+
+int res_sample_browse(struct res_sample *res_samples, int num_res,
+		      struct perf_evsel *evsel, enum rstype rstype)
+{
+	char **names;
+	int i, n;
+	int choice;
+	char *cmd;
+	char pbuf[256], tidbuf[32], cpubuf[32];
+	const char *perf = perf_exe(pbuf, sizeof pbuf);
+	char trange[128], tsample[64];
+	struct res_sample *r;
+	char extra_format[256];
+
+	/* For now since ui__popup_menu doesn't like lists that don't fit */
+	num_res = max(min(SLtt_Screen_Rows - 4, num_res), 0);
+
+	names = calloc(num_res, sizeof(char *));
+	if (!names)
+		return -1;
+	for (i = 0; i < num_res; i++) {
+		char tbuf[64];
+
+		timestamp__scnprintf_nsec(res_samples[i].time, tbuf, sizeof tbuf);
+		if (asprintf(&names[i], "%s: CPU %d tid %d", tbuf,
+			     res_samples[i].cpu, res_samples[i].tid) < 0) {
+			while (--i >= 0)
+				free(names[i]);
+			free(names);
+			return -1;
+		}
+	}
+	choice = ui__popup_menu(num_res, names);
+	for (i = 0; i < num_res; i++)
+		free(names[i]);
+	free(names);
+
+	if (choice < 0 || choice >= num_res)
+		return -1;
+	r = &res_samples[choice];
+
+	n = timestamp__scnprintf_nsec(r->time - context_len, trange, sizeof trange);
+	trange[n++] = ',';
+	timestamp__scnprintf_nsec(r->time + context_len, trange + n, sizeof trange - n);
+
+	timestamp__scnprintf_nsec(r->time, tsample, sizeof tsample);
+
+	attr_to_script(extra_format, &evsel->attr);
+
+	if (asprintf(&cmd, "%s script %s%s --time %s %s%s %s%s --ns %s %s %s %s %s | less +/%s",
+		     perf,
+		     input_name ? "-i " : "",
+		     input_name ? input_name : "",
+		     trange,
+		     r->cpu >= 0 ? "--cpu " : "",
+		     r->cpu >= 0 ? (sprintf(cpubuf, "%d", r->cpu), cpubuf) : "",
+		     r->tid ? "--tid " : "",
+		     r->tid ? (sprintf(tidbuf, "%d", r->tid), tidbuf) : "",
+		     extra_format,
+		     rstype == A_ASM ? "-F +insn --xed" :
+		     rstype == A_SOURCE ? "-F +srcline,+srccode" : "",
+		     symbol_conf.inline_name ? "--inline" : "",
+		     "--show-lost-events ",
+		     r->tid ? "--show-switch-events --show-task-events " : "",
+		     tsample) < 0)
+		return -1;
+	run_script(cmd);
+	free(cmd);
+	return 0;
+}

tools/perf/ui/browsers/scripts.c

···
 	return ret;
 }
 
-static void run_script(char *cmd)
+void run_script(char *cmd)
 {
 	pr_debug("Running %s\n", cmd);
 	SLang_reset_tty();

tools/perf/util/hist.c

···
 			goto err_rawdata;
 	}
 
+	if (symbol_conf.res_sample) {
+		he->res_samples = calloc(sizeof(struct res_sample),
+					symbol_conf.res_sample);
+		if (!he->res_samples)
+			goto err_srcline;
+	}
+
 	INIT_LIST_HEAD(&he->pairs.node);
 	thread__get(he->thread);
 	he->hroot_in  = RB_ROOT_CACHED;
···
 		he->leaf = true;
 
 	return 0;
+
+err_srcline:
+	free(he->srcline);
 
 err_rawdata:
 	free(he->raw_data);
···
 	return he;
 }
 
+static unsigned random_max(unsigned high)
+{
+	unsigned thresh = -high % high;
+	for (;;) {
+		unsigned r = random();
+		if (r >= thresh)
+			return r % high;
+	}
+}
+
+static void hists__res_sample(struct hist_entry *he, struct perf_sample *sample)
+{
+	struct res_sample *r;
+	int j;
+
+	if (he->num_res < symbol_conf.res_sample) {
+		j = he->num_res++;
+	} else {
+		j = random_max(symbol_conf.res_sample);
+	}
+	r = &he->res_samples[j];
+	r->time = sample->time;
+	r->cpu = sample->cpu;
+	r->tid = sample->tid;
+}
+
 static struct hist_entry*
 __hists__add_entry(struct hists *hists,
 		   struct addr_location *al,
···
 
 	if (!hists->has_callchains && he && he->callchain_size != 0)
 		hists->has_callchains = true;
+	if (he && symbol_conf.res_sample)
+		hists__res_sample(he, sample);
 	return he;
 }
 
···
 		mem_info__zput(he->mem_info);
 	}
 
+	zfree(&he->res_samples);
 	zfree(&he->stat_acc);
 	free_srcline(he->srcline);
 	if (he->srcfile && he->srcfile[0])

tools/perf/util/hist.h

···
 };
 
 struct annotation_options;
+struct res_sample;
+
+enum rstype {
+	A_NORMAL,
+	A_ASM,
+	A_SOURCE
+};
 
 #ifdef HAVE_SLANG_SUPPORT
 #include "../ui/keysyms.h"
···
 				  struct annotation_options *annotation_options);
 
 int script_browse(const char *script_opt, struct perf_evsel *evsel);
+
+void run_script(char *cmd);
+int res_sample_browse(struct res_sample *res_samples, int num_res,
+		      struct perf_evsel *evsel, enum rstype rstype);
+void res_sample_init(void);
 #else
 static inline
 int perf_evlist__tui_browse_hists(struct perf_evlist *evlist __maybe_unused,
···
 {
 	return 0;
 }
+
+static inline int res_sample_browse(struct res_sample *res_samples __maybe_unused,
+				    int num_res __maybe_unused,
+				    struct perf_evsel *evsel __maybe_unused,
+				    enum rstype rstype __maybe_unused)
+{
+	return 0;
+}
+
+static inline void res_sample_init(void) {}
 
 #define K_LEFT  -1000
 #define K_RIGHT -2000

tools/perf/util/sort.h

···
 extern enum sort_type sort__first_dimension;
 extern const char default_mem_sort_order[];
 
+struct res_sample {
+	u64 time;
+	int cpu;
+	int tid;
+};
+
 struct he_stat {
 	u64			period;
 	u64			period_sys;
···
 	struct mem_info		*mem_info;
 	void			*raw_data;
 	u32			raw_size;
+	int			num_res;
+	struct res_sample	*res_samples;
 	void			*trace_output;
 	struct perf_hpp_list	*hpp_list;
 	struct hist_entry	*parent_he;

tools/perf/util/symbol.c

···
 	.symfs			= "",
 	.event_group		= true,
 	.inline_name		= true,
+	.res_sample		= 0,
 };
 
 static enum dso_binary_type binary_type_symtab[] = {

tools/perf/util/symbol_conf.h

···
 	struct intlist	*pid_list,
 			*tid_list;
 	const char	*symfs;
+	int		res_sample;
 };
 
 extern struct symbol_conf symbol_conf;