perf record: Extend trace writing to multi AIO

Multi AIO trace writing allows caching more kernel data into userspace
memory postponing trace writing for the sake of overall profiling data
thruput increase. It could be seen as kernel data buffer extension into
userspace memory.

With an --aio option value different from 0 (default value is 1) the
tool has capability to cache more and more data into user space along
with delegating spill to AIO.

That allows avoiding to suspend at record__aio_sync() between calls of
record__mmap_read_evlist() and increases profiling data thruput at the
cost of userspace memory.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/050bb053-e7f3-aa83-fde7-f27ff90be7f6@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 52 insertions, 15 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 408d6477c960..4736dc96c4ca 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -196,16 +196,35 @@ static int record__aio_complete(struct perf_mmap *md, struct aiocb *cblock)
 	return rc;
 }
 
-static void record__aio_sync(struct perf_mmap *md)
+static int record__aio_sync(struct perf_mmap *md, bool sync_all)
 {
-	struct aiocb *cblock = &md->aio.cblock;
+	struct aiocb **aiocb = md->aio.aiocb;
+	struct aiocb *cblocks = md->aio.cblocks;
 	struct timespec timeout = { 0, 1000 * 1000  * 1 }; /* 1ms */
+	int i, do_suspend;
 
 	do {
-		if (cblock->aio_fildes == -1 || record__aio_complete(md, cblock))
-			return;
+		do_suspend = 0;
+		for (i = 0; i < md->aio.nr_cblocks; ++i) {
+			if (cblocks[i].aio_fildes == -1 || record__aio_complete(md, &cblocks[i])) {
+				if (sync_all)
+					aiocb[i] = NULL;
+				else
+					return i;
+			} else {
+				/*
+				 * Started aio write is not complete yet
+				 * so it has to be waited before the
+				 * next allocation.
+				 */
+				aiocb[i] = &cblocks[i];
+				do_suspend = 1;
+			}
+		}
+		if (!do_suspend)
+			return -1;
 
-		while (aio_suspend((const struct aiocb**)&cblock, 1, &timeout)) {
+		while (aio_suspend((const struct aiocb **)aiocb, md->aio.nr_cblocks, &timeout)) {
 			if (!(errno == EAGAIN || errno == EINTR))
 				pr_err("failed to sync perf data, error: %m\n");
 		}
@@ -252,28 +271,36 @@ static void record__aio_mmap_read_sync(struct record *rec)
 		struct perf_mmap *map = &maps[i];
 
 		if (map->base)
-			record__aio_sync(map);
+			record__aio_sync(map, true);
 	}
 }
 
 static int nr_cblocks_default = 1;
+static int nr_cblocks_max = 4;
 
 static int record__aio_parse(const struct option *opt,
-			     const char *str __maybe_unused,
+			     const char *str,
 			     int unset)
 {
 	struct record_opts *opts = (struct record_opts *)opt->value;
 
-	if (unset)
+	if (unset) {
 		opts->nr_cblocks = 0;
-	else
-		opts->nr_cblocks = nr_cblocks_default;
+	} else {
+		if (str)
+			opts->nr_cblocks = strtol(str, NULL, 0);
+		if (!opts->nr_cblocks)
+			opts->nr_cblocks = nr_cblocks_default;
+	}
 
 	return 0;
 }
 #else /* HAVE_AIO_SUPPORT */
-static void record__aio_sync(struct perf_mmap *md __maybe_unused)
+static int nr_cblocks_max = 0;
+
+static int record__aio_sync(struct perf_mmap *md __maybe_unused, bool sync_all __maybe_unused)
 {
+	return -1;
 }
 
 static int record__aio_pushfn(void *to __maybe_unused, struct aiocb *cblock __maybe_unused,
@@ -728,12 +755,13 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
 					goto out;
 				}
 			} else {
+				int idx;
 				/*
 				 * Call record__aio_sync() to wait till map->data buffer
 				 * becomes available after previous aio write request.
 				 */
-				record__aio_sync(map);
-				if (perf_mmap__aio_push(map, rec, record__aio_pushfn, &off) != 0) {
+				idx = record__aio_sync(map, false);
+				if (perf_mmap__aio_push(map, rec, idx, record__aio_pushfn, &off) != 0) {
 					record__aio_set_pos(trace_fd, off);
 					rc = -1;
 					goto out;
@@ -1503,6 +1531,13 @@ static int perf_record_config(const char *var, const char *value, void *cb)
 		var = "call-graph.record-mode";
 		return perf_default_config(var, value, cb);
 	}
+#ifdef HAVE_AIO_SUPPORT
+	if (!strcmp(var, "record.aio")) {
+		rec->opts.nr_cblocks = strtol(value, NULL, 0);
+		if (!rec->opts.nr_cblocks)
+			rec->opts.nr_cblocks = nr_cblocks_default;
+	}
+#endif
 
 	return 0;
 }
@@ -1909,8 +1944,8 @@ static struct option __record_options[] = {
 	OPT_BOOLEAN(0, "dry-run", &dry_run,
 		    "Parse options then exit"),
 #ifdef HAVE_AIO_SUPPORT
-	OPT_CALLBACK_NOOPT(0, "aio", &record.opts,
-		     NULL, "Enable asynchronous trace writing mode",
+	OPT_CALLBACK_OPTARG(0, "aio", &record.opts,
+		     &nr_cblocks_default, "n", "Use <n> control blocks in asynchronous trace writing mode (default: 1, max: 4)",
 		     record__aio_parse),
 #endif
 	OPT_END()
@@ -2105,6 +2140,8 @@ int cmd_record(int argc, const char **argv)
 		goto out;
 	}
 
+	if (rec->opts.nr_cblocks > nr_cblocks_max)
+		rec->opts.nr_cblocks = nr_cblocks_max;
 	if (verbose > 0)
 		pr_info("nr_cblocks: %d\n", rec->opts.nr_cblocks);