perf trace: Implement syscall summary in BPF

When -s/--summary option is used, it doesn't need (augmented) arguments
of syscalls.  Let's skip the augmentation and load another small BPF
program to collect the statistics in the kernel instead of copying the
data to the ring-buffer to calculate the stats in userspace.  This will
be much more light-weight than the existing approach and remove any lost
events.

Let's add a new option --bpf-summary to control this behavior.  I cannot
make it default because there's no way to get e_machine in the BPF which
is needed for detecting different ABIs like 32-bit compat mode.

No functional changes intended except for no more LOST events. :)

  $ sudo ./perf trace -as --summary-mode=total --bpf-summary sleep 1

   Summary of events:

   total, 6194 events

     syscall            calls  errors  total       min       avg       max       stddev
                                       (msec)    (msec)    (msec)    (msec)        (%)
     --------------- --------  ------ -------- --------- --------- ---------     ------
     epoll_wait           561      0  4530.843     0.000     8.076   520.941     18.75%
     futex                693     45  4317.231     0.000     6.230   500.077     21.98%
     poll                 300      0  1040.109     0.000     3.467   120.928     17.02%
     clock_nanosleep        1      0  1000.172  1000.172  1000.172  1000.172      0.00%
     ppoll                360      0   872.386     0.001     2.423   253.275     41.91%
     epoll_pwait           14      0   384.349     0.001    27.453   380.002     98.79%
     pselect6              14      0   108.130     7.198     7.724     8.206      0.85%
     nanosleep             39      0    43.378     0.069     1.112    10.084     44.23%
     ...

Reviewed-by: Howard Chu <[email protected]>
Signed-off-by: Namhyung Kim <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Howard Chu <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Song Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[ Added fixup sent from Namhyung in response to my report to make it also dependent on CONFIG_TRACE ]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: namhyung

tools/perf/Documentation/perf-trace.txt

@@ -251,6 +251,12 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
 	pretty-printing serves as a fallback to hand-crafted pretty printers, as the latter can
 	better pretty-print integer flags and struct pointers.
 
+--bpf-summary::
+	Collect system call statistics in BPF.  This is only for live mode and
+	works well with -s/--summary option where no argument information is
+	required.
+
+
 PAGEFAULTS
 ----------
 

tools/perf/Makefile.perf

@@ -1175,7 +1175,7 @@ SKELETONS += $(SKEL_OUT)/bperf_leader.skel.h $(SKEL_OUT)/bperf_follower.skel.h
 SKELETONS += $(SKEL_OUT)/bperf_cgroup.skel.h $(SKEL_OUT)/func_latency.skel.h
 SKELETONS += $(SKEL_OUT)/off_cpu.skel.h $(SKEL_OUT)/lock_contention.skel.h
 SKELETONS += $(SKEL_OUT)/kwork_trace.skel.h $(SKEL_OUT)/sample_filter.skel.h
-SKELETONS += $(SKEL_OUT)/kwork_top.skel.h
+SKELETONS += $(SKEL_OUT)/kwork_top.skel.h $(SKEL_OUT)/syscall_summary.skel.h
 SKELETONS += $(SKEL_OUT)/bench_uprobe.skel.h
 SKELETONS += $(SKEL_OUT)/augmented_raw_syscalls.skel.h
 

tools/perf/builtin-trace.c

@@ -55,6 +55,7 @@
 #include "util/thread_map.h"
 #include "util/stat.h"
 #include "util/tool.h"
+#include "util/trace.h"
 #include "util/util.h"
 #include "trace/beauty/beauty.h"
 #include "trace-event.h"
@@ -141,12 +142,6 @@ struct syscall_fmt {
 	bool	   hexret;
 };
 
-enum summary_mode {
-	SUMMARY__NONE = 0,
-	SUMMARY__BY_TOTAL,
-	SUMMARY__BY_THREAD,
-};
-
 struct trace {
 	struct perf_tool	tool;
 	struct {
@@ -205,7 +200,7 @@ struct trace {
 	} stats;
 	unsigned int		max_stack;
 	unsigned int		min_stack;
-	enum summary_mode	summary_mode;
+	enum trace_summary_mode	summary_mode;
 	int			raw_augmented_syscalls_args_size;
 	bool			raw_augmented_syscalls;
 	bool			fd_path_disabled;
@@ -234,6 +229,7 @@ struct trace {
 	bool			force;
 	bool			vfs_getname;
 	bool			force_btf;
+	bool			summary_bpf;
 	int			trace_pgfaults;
 	char			*perfconfig_events;
 	struct {
@@ -2614,6 +2610,9 @@ static void thread__update_stats(struct thread *thread, struct thread_trace *ttr
 	struct syscall_stats *stats = NULL;
 	u64 duration = 0;
 
+	if (trace->summary_bpf)
+		return;
+
 	if (trace->summary_mode == SUMMARY__BY_TOTAL)
 		syscall_stats = trace->syscall_stats;
 
@@ -4377,6 +4376,14 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 
 	trace->live = true;
 
+	if (trace->summary_bpf) {
+		if (trace_prepare_bpf_summary(trace->summary_mode) < 0)
+			goto out_delete_evlist;
+
+		if (trace->summary_only)
+			goto create_maps;
+	}
+
 	if (!trace->raw_augmented_syscalls) {
 		if (trace->trace_syscalls && trace__add_syscall_newtp(trace))
 			goto out_error_raw_syscalls;
@@ -4435,6 +4442,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 	if (trace->cgroup)
 		evlist__set_default_cgroup(trace->evlist, trace->cgroup);
 
+create_maps:
 	err = evlist__create_maps(evlist, &trace->opts.target);
 	if (err < 0) {
 		fprintf(trace->output, "Problems parsing the target to trace, check your options!\n");
@@ -4447,7 +4455,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 		goto out_delete_evlist;
 	}
 
-	if (trace->summary_mode == SUMMARY__BY_TOTAL) {
+	if (trace->summary_mode == SUMMARY__BY_TOTAL && !trace->summary_bpf) {
 		trace->syscall_stats = alloc_syscall_stats();
 		if (trace->syscall_stats == NULL)
 			goto out_delete_evlist;
@@ -4535,9 +4543,11 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 	if (err < 0)
 		goto out_error_apply_filters;
 
-	err = evlist__mmap(evlist, trace->opts.mmap_pages);
-	if (err < 0)
-		goto out_error_mmap;
+	if (!trace->summary_only || !trace->summary_bpf) {
+		err = evlist__mmap(evlist, trace->opts.mmap_pages);
+		if (err < 0)
+			goto out_error_mmap;
+	}
 
 	if (!target__none(&trace->opts.target) && !trace->opts.target.initial_delay)
 		evlist__enable(evlist);
@@ -4550,6 +4560,9 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 		evlist__enable(evlist);
 	}
 
+	if (trace->summary_bpf)
+		trace_start_bpf_summary();
+
 	trace->multiple_threads = perf_thread_map__pid(evlist->core.threads, 0) == -1 ||
 		perf_thread_map__nr(evlist->core.threads) > 1 ||
 		evlist__first(evlist)->core.attr.inherit;
@@ -4617,12 +4630,17 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 
 	evlist__disable(evlist);
 
+	if (trace->summary_bpf)
+		trace_end_bpf_summary();
+
 	if (trace->sort_events)
 		ordered_events__flush(&trace->oe.data, OE_FLUSH__FINAL);
 
 	if (!err) {
 		if (trace->summary) {
-			if (trace->summary_mode == SUMMARY__BY_TOTAL)
+			if (trace->summary_bpf)
+				trace_print_bpf_summary(trace->output);
+			else if (trace->summary_mode == SUMMARY__BY_TOTAL)
 				trace__fprintf_total_summary(trace, trace->output);
 			else
 				trace__fprintf_thread_summary(trace, trace->output);
@@ -4638,6 +4656,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 	}
 
 out_delete_evlist:
+	trace_cleanup_bpf_summary();
 	delete_syscall_stats(trace->syscall_stats);
 	trace__symbols__exit(trace);
 	evlist__free_syscall_tp_fields(evlist);
@@ -5473,6 +5492,7 @@ int cmd_trace(int argc, const char **argv)
 		     "start"),
 	OPT_BOOLEAN(0, "force-btf", &trace.force_btf, "Prefer btf_dump general pretty printer"
 		       "to customized ones"),
+	OPT_BOOLEAN(0, "bpf-summary", &trace.summary_bpf, "Summary syscall stats in BPF"),
 	OPTS_EVSWITCH(&trace.evswitch),
 	OPT_END()
 	};
@@ -5564,6 +5584,16 @@ int cmd_trace(int argc, const char **argv)
 		goto skip_augmentation;
 	}
 
+	if (trace.summary_bpf) {
+		if (!trace.opts.target.system_wide) {
+			/* TODO: Add filters in the BPF to support other targets. */
+			pr_err("Error: --bpf-summary only works for system-wide mode.\n");
+			goto out;
+		}
+		if (trace.summary_only)
+			goto skip_augmentation;
+	}
+
 	trace.skel = augmented_raw_syscalls_bpf__open();
 	if (!trace.skel) {
 		pr_debug("Failed to open augmented syscalls BPF skeleton");

tools/perf/util/Build

@@ -173,6 +173,10 @@ perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf-filter-flex.o
 perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf-filter-bison.o
 perf-util-$(CONFIG_PERF_BPF_SKEL) += btf.o
 
+ifeq ($(CONFIG_TRACE),y)
+  perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf-trace-summary.o
+endif
+
 ifeq ($(CONFIG_LIBTRACEEVENT),y)
   perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf_lock_contention.o
 endif