perf annotate: Add --skip-empty option

Like in 'perf report', we want to hide empty events in the 'perf annotate'
output. This is consistent when the option is set in perf report.

For example, the following command would use 3 events including dummy.

$ perf mem record -a -- perf test -w noploop

$ perf evlist
cpu/mem-loads,ldlat=30/P
cpu/mem-stores/P
dummy:u

Just using perf annotate with --group will show the all 3 events.

$ perf annotate --group --stdio | head
Percent | Source code & Disassembly of ...
--------------------------------------------------------------
: 0 0xe060 <_dl_relocate_object>:
0.00 0.00 0.00 : e060: pushq %rbp
0.00 0.00 0.00 : e061: movq %rsp, %rbp
0.00 0.00 0.00 : e064: pushq %r15
0.00 0.00 0.00 : e066: movq %rdi, %r15
0.00 0.00 0.00 : e069: pushq %r14
0.00 0.00 0.00 : e06b: pushq %r13
0.00 0.00 0.00 : e06d: movl %edx, %r13d

Now with --skip-empty, it'll hide the last dummy event.

$ perf annotate --group --stdio --skip-empty | head
Percent | Source code & Disassembly of ...
------------------------------------------------------
: 0 0xe060 <_dl_relocate_object>:
0.00 0.00 : e060: pushq %rbp
0.00 0.00 : e061: movq %rsp, %rbp
0.00 0.00 : e064: pushq %r15
0.00 0.00 : e066: movq %rdi, %r15
0.00 0.00 : e069: pushq %r14
0.00 0.00 : e06b: pushq %r13
0.00 0.00 : e06d: movl %edx, %r13d

Committer testing:

root@x1:~# perf evlist
cpu_atom/mem-loads,ldlat=30/P
cpu_atom/mem-stores/P
dummy:u
root@x1:~#

Before:

root@x1:~# perf annotate --group --stdio2 do_lookup_x | head -25
Samples: 20 of events 'cpu_atom/mem-loads,ldlat=30/P, cpu_atom/mem-stores/P, dummy:u', 4000 Hz, Event count (approx.): 769079, [percent: local period]
do_lookup_x() /usr/lib64/ld-linux-x86-64.so.2
Percent 0x9900 <do_lookup_x>:
pushq %rbp
movq %rsp,%rbp
pushq %r15
pushq %r14
pushq %r13
pushq %r12
pushq %rbx
subq $0x88,%rsp
movq %rdi,-0x50(%rbp)
movl 8(%r9),%edi
movq 0x10(%rbp),%r12
movq 0x28(%rbp),%r10
movq %rdx,-0x70(%rbp)
movq %rcx,-0x58(%rbp)
movq %rdi,%r11
0.00 5.73 0.00 movq %r8,-0x68(%rbp)
movq (%r9),%r8
movl %esi,%eax
8.30 0.00 0.00 movl 0x30(%rbp),%r9d
movl %esi,%r15d
shrl $6, %eax
movq %r8,%r13
root@x1:~#

After:

root@x1:~# perf annotate --group --skip-empty --stdio2 do_lookup_x | head -25
Samples: 20 of events 'cpu_atom/mem-loads,ldlat=30/P, cpu_atom/mem-stores/P', 4000 Hz, Event count (approx.): 769079, [percent: local period]
do_lookup_x() /usr/lib64/ld-linux-x86-64.so.2
Percent 0x9900 <do_lookup_x>:
pushq %rbp
movq %rsp,%rbp
pushq %r15
pushq %r14
pushq %r13
pushq %r12
pushq %rbx
subq $0x88,%rsp
movq %rdi,-0x50(%rbp)
movl 8(%r9),%edi
movq 0x10(%rbp),%r12
movq 0x28(%rbp),%r10
movq %rdx,-0x70(%rbp)
movq %rcx,-0x58(%rbp)
movq %rdi,%r11
0.00 5.73 movq %r8,-0x68(%rbp)
movq (%r9),%r8
movl %esi,%eax
8.30 0.00 movl 0x30(%rbp),%r9d
movl %esi,%r15d
shrl $6, %eax
movq %r8,%r13
root@x1:~#

Signed-off-by: Namhyung Kim <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-annotate.txt

···
 --type-stat::
 	Show stats for the data type annotation.
 
+--skip-empty::
+	Do not display empty (or dummy) events.
+
 
 SEE ALSO
 --------

tools/perf/builtin-annotate.c

···
 		    "Show stats for the data type annotation"),
 	OPT_BOOLEAN(0, "insn-stat", &annotate.insn_stat,
 		    "Show instruction stats for the data type annotation"),
+	OPT_BOOLEAN(0, "skip-empty", &symbol_conf.skip_empty,
+		    "Do not display empty (or dummy) events in the output"),
 	OPT_END()
 	};
 	int ret;

tools/perf/util/annotate.c

···
 
 			BUG_ON(i >= al->data_nr);
 
+			if (symbol_conf.skip_empty &&
+			    evsel__hists(evsel)->stats.nr_samples == 0)
+				continue;
+
 			data = &al->data[i++];
 
 			calc_percent(notes, evsel, data, al->offset, end);
···
 		.options	= &annotate_opts,
 	};
 	struct arch *arch = NULL;
-	int err;
+	int err, nr;
 
 	err = evsel__get_arch(evsel, &arch);
 	if (err < 0)
···
 			return -1;
 	}
 
-	if (evsel__is_group_event(evsel))
-		notes->src->nr_events = evsel->core.nr_members;
-	else
-		notes->src->nr_events = 1;
+	nr = 0;
+	if (evsel__is_group_event(evsel)) {
+		struct evsel *pos;
+
+		for_each_group_evsel(pos, evsel) {
+			if (symbol_conf.skip_empty &&
+			    evsel__hists(pos)->stats.nr_samples == 0)
+				continue;
+			nr++;
+		}
+	}
+	notes->src->nr_events = nr ? nr : 1;
 
 	if (annotate_opts.full_addr)
 		notes->src->start = map__objdump_2mem(ms->map, ms->sym->start);