[PATCH v6 1/2]: perf util: map data buffer for preserving collected data

[PATCH v6 1/2]: perf util: map data buffer for preserving collected data

[Alexey Budankov]

The map->data buffers are used to preserve map->base profiling data 
for writing to disk. AIO map->cblocks are used to queue corresponding 
map->data buffers for asynchronous writing. map->cblocks objects are 
located in the last page of every map->data buffer.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 Changes in v6:
  - adjusted setting of priorities for cblocks;
 Changes in v5:
  - reshaped layout of data structures;
  - implemented --aio option;
 Changes in v4:
  - converted mmap()/munmap() to malloc()/free() for mmap->data buffer management 
 Changes in v2:
  - converted zalloc() to calloc() for allocation of mmap_aio array,
  - cleared typo and adjusted fallback branch code;
--- 
 tools/perf/builtin-record.c | 12 +++++++++-
 tools/perf/perf.h           |  1 +
 tools/perf/util/evlist.c    |  7 +++---
 tools/perf/util/evlist.h    |  3 ++-
 tools/perf/util/mmap.c      | 53 +++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/mmap.h      |  6 ++++-
 6 files changed, 76 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 22ebeb92ac51..8eb093f8d4d5 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -326,7 +326,8 @@ static int record__mmap_evlist(struct record *rec,
 
 	if (perf_evlist__mmap_ex(evlist, opts->mmap_pages,
 				 opts->auxtrace_mmap_pages,
-				 opts->auxtrace_snapshot_mode) < 0) {
+				 opts->auxtrace_snapshot_mode,
+				 opts->nr_cblocks) < 0) {
 		if (errno == EPERM) {
 			pr_err("Permission error mapping pages.\n"
 			       "Consider increasing "
@@ -1519,6 +1520,7 @@ static struct record record = {
 			.default_per_cpu = true,
 		},
 		.proc_map_timeout     = 500,
+		.nr_cblocks	      = 2
 	},
 	.tool = {
 		.sample		= process_sample_event,
@@ -1678,6 +1680,8 @@ static struct option __record_options[] = {
 			  "signal"),
 	OPT_BOOLEAN(0, "dry-run", &dry_run,
 		    "Parse options then exit"),
+	OPT_INTEGER(0, "aio", &record.opts.nr_cblocks,
+		    "asynchronous trace write operations (min: 1, max: 32, default: 2)"),
 	OPT_END()
 };
 
@@ -1870,6 +1874,12 @@ int cmd_record(int argc, const char **argv)
 		goto out;
 	}
 
+	if (!(1 <= rec->opts.nr_cblocks && rec->opts.nr_cblocks <= 32)) {
+		if (verbose > 0)
+			pr_warning("Asynchronous trace writes reset to default.\n");
+		rec->opts.nr_cblocks = 2;
+	}
+
 	err = __cmd_record(&record, argc, argv);
 out:
 	perf_evlist__delete(rec->evlist);
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 21bf7f5a3cf5..0a1ae2ae567a 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -82,6 +82,7 @@ struct record_opts {
 	bool         use_clockid;
 	clockid_t    clockid;
 	unsigned int proc_map_timeout;
+	int	     nr_cblocks;
 };
 
 struct option;
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index e7a4b31a84fb..08be79650a85 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1018,7 +1018,8 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
  */
 int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 			 unsigned int auxtrace_pages,
-			 bool auxtrace_overwrite)
+			 bool auxtrace_overwrite,
+			 int nr_cblocks)
 {
 	struct perf_evsel *evsel;
 	const struct cpu_map *cpus = evlist->cpus;
@@ -1028,7 +1029,7 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 	 * Its value is decided by evsel's write_backward.
 	 * So &mp should not be passed through const pointer.
 	 */
-	struct mmap_params mp;
+	struct mmap_params mp = { .nr_cblocks = nr_cblocks };
 
 	if (!evlist->mmap)
 		evlist->mmap = perf_evlist__alloc_mmap(evlist, false);
@@ -1060,7 +1061,7 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 
 int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages)
 {
-	return perf_evlist__mmap_ex(evlist, pages, 0, false);
+	return perf_evlist__mmap_ex(evlist, pages, 0, false, 2);
 }
 
 int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target)
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index dc66436add98..a94d3c613254 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -162,7 +162,8 @@ unsigned long perf_event_mlock_kb_in_pages(void);
 
 int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 			 unsigned int auxtrace_pages,
-			 bool auxtrace_overwrite);
+			 bool auxtrace_overwrite,
+			 int nr_cblocks);
 int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages);
 void perf_evlist__munmap(struct perf_evlist *evlist);
 
diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index fc832676a798..384d17cd1379 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -155,6 +155,14 @@ void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __mayb
 
 void perf_mmap__munmap(struct perf_mmap *map)
 {
+	int i;
+	if (map->data) {
+		for (i = 0; i < map->nr_cblocks; ++i)
+			zfree(&(map->data[i]));
+		zfree(&(map->data));
+	}
+	if (map->cblocks)
+		zfree(&(map->cblocks));
 	if (map->base != NULL) {
 		munmap(map->base, perf_mmap__mmap_len(map));
 		map->base = NULL;
@@ -166,6 +174,7 @@ void perf_mmap__munmap(struct perf_mmap *map)
 
 int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
 {
+	int i;
 	/*
 	 * The last one will be done at perf_mmap__consume(), so that we
 	 * make sure we don't prevent tools from consuming every last event in
@@ -190,6 +199,50 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
 		map->base = NULL;
 		return -1;
 	}
+	map->nr_cblocks = mp->nr_cblocks;
+	map->cblocks = calloc(map->nr_cblocks, sizeof(struct aiocb*));
+	if (!map->cblocks) {
+		pr_debug2("failed to allocate perf event data buffers, error %d\n",
+				errno);
+		return -1;
+	}
+	map->data = calloc(map->nr_cblocks, sizeof(void*));
+	if (map->data) {
+		int delta_max = sysconf(_SC_AIO_PRIO_DELTA_MAX);
+		for (i = 0; i < map->nr_cblocks; ++i) {
+			map->data[i] = malloc(perf_mmap__mmap_len(map));
+			if (map->data[i]) {
+				int prio;
+				unsigned char *data = map->data[i];
+				map->cblocks[i] = (struct aiocb *)&data[map->mask + 1];
+				memset(map->cblocks[i], 0, sizeof(struct aiocb));
+				/* Use cblock.aio_fildes value different from -1
+				 * to denote started aio write operation on the
+				 * cblock so it requires explicit record__aio_sync()
+				 * call prior the cblock may be reused again.
+				 */
+				map->cblocks[i]->aio_fildes = -1;
+				/* Allocate cblocks with decreasing priority to
+				 * have faster aio_write() calls because queued
+				 * requests are kept in separate per-prio queues
+				 * and adding a new request iterates thru shorter
+				 * per-prio list.
+				 */
+				prio = delta_max - i;
+				if (prio < 0)
+					prio = 0;
+				map->cblocks[i]->aio_reqprio = prio;
+			} else {
+				pr_debug2("failed to allocate perf event data buffer, error %d\n",
+						errno);
+				return -1;
+			}
+		}
+	} else {
+		pr_debug2("failed to alloc perf event data buffers, error %d\n",
+				errno);
+		return -1;
+	}
 	map->fd = fd;
 
 	if (auxtrace_mmap__mmap(&map->auxtrace_mmap,
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index d82294db1295..4a9bb0ecae4f 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -6,6 +6,7 @@
 #include <linux/types.h>
 #include <asm/barrier.h>
 #include <stdbool.h>
+#include <aio.h>
 #include "auxtrace.h"
 #include "event.h"
 
@@ -25,6 +26,9 @@ struct perf_mmap {
 	bool		 overwrite;
 	struct auxtrace_mmap auxtrace_mmap;
 	char		 event_copy[PERF_SAMPLE_MAX_SIZE] __aligned(8);
+	void 		 **data;
+	struct aiocb	 **cblocks;
+	int 		 nr_cblocks;
 };
 
 /*
@@ -56,7 +60,7 @@ enum bkw_mmap_state {
 };
 
 struct mmap_params {
-	int			    prot, mask;
+	int			    prot, mask, nr_cblocks;
 	struct auxtrace_mmap_params auxtrace_mp;
 };

[PATCH v6 2/2]: perf record: enable asynchronous trace writing

[Alexey Budankov]

record__aio_sync() allocates index of free map->data buffer for 
a cpu buffer or blocks till completion of any started operation 
and then proceeds.

Trace file offset is calculated and updated linearly prior
enqueuing aio write at record__pushfn().

record__mmap_read_sync() implements a barrier for all incomplete
aio write requests per-cpu per aio data.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 Changes in v6:
 - handled errno == EAGAIN case from aio_write();
 Changes in v5:
 - data loss metrics decreased from 25% to 2x in trialed configuration;
 - avoided nanosleep() prior calling aio_suspend();
 - switched to per cpu multi record__aio_sync() aio
 - record_mmap_read_sync() now does global barrier just before 
   switching trace file or collection stop;
 - resolved livelock on perf record -e intel_pt// -- dd if=/dev/zero of=/dev/null count=100000
 Changes in v4:
 - converted void *bf to struct perf_mmap *md in signatures
 - written comment in perf_mmap__push() just before perf_mmap__get();
 - written comment in record__mmap_read_sync() on possible restarting 
   of aio_write() operation and releasing perf_mmap object after all;
 - added perf_mmap__put() for the cases of failed aio_write();
 Changes in v3:
 - written comments about nanosleep(0.5ms) call prior aio_suspend()
   to cope with intrusiveness of its implementation in glibc;
 - written comments about rationale behind coping profiling data 
   into mmap->data buffer;
---
 tools/perf/builtin-record.c | 182 +++++++++++++++++++++++++++++++++++++++++++-
 tools/perf/util/mmap.c      |  57 ++++++++++----
 tools/perf/util/mmap.h      |   4 +-
 3 files changed, 223 insertions(+), 20 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 8eb093f8d4d5..78965b3737a9 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -121,6 +121,91 @@ static int record__write(struct record *rec, void *bf, size_t size)
 	return 0;
 }
 
+static int record__aio_write(struct aiocb *cblock, int trace_fd,
+		void *buf, size_t size, off_t off)
+{
+	int rc;
+
+	cblock->aio_fildes = trace_fd;
+	cblock->aio_buf    = buf;
+	cblock->aio_nbytes = size;
+	cblock->aio_offset = off;
+	cblock->aio_sigevent.sigev_notify = SIGEV_NONE;
+
+	do {
+		rc = aio_write(cblock);
+		if (rc == 0) {
+			break;
+		} else if (errno != EAGAIN) {
+			cblock->aio_fildes = -1;
+			pr_err("failed to queue perf data, error: %m\n");
+			break;
+		}
+	} while (1);
+
+	return rc;
+}
+
+static int record__aio_sync(struct perf_mmap *md)
+{
+	void *rem_buf;
+	off_t rem_off;
+	size_t rem_size;
+	ssize_t aio_ret, written;
+	int i, aio_errno, do_suspend, idx = -1;
+	struct aiocb **cblocks = md->cblocks;
+	struct timespec timeout = { 0, 1000 * 1000  * 1 }; // 1ms
+
+	for (i = 0; i < md->nr_cblocks; ++i)
+		if (cblocks[i]->aio_fildes == -1)
+			return i;
+
+	do {
+		do_suspend = 0;
+		if (aio_suspend((const struct aiocb**)cblocks, md->nr_cblocks, &timeout)) {
+			if (!(errno == EAGAIN || errno == EINTR))
+				pr_err("failed to sync perf data, error: %m\n");
+			do_suspend = 1;
+			continue;
+		}
+		for (i = 0; i < md->nr_cblocks; ++i) {
+			aio_errno = aio_error(cblocks[i]);
+			if (aio_errno == EINPROGRESS)
+				continue;
+			written = aio_ret = aio_return(cblocks[i]);
+			if (aio_ret < 0) {
+				if (aio_errno != EINTR)
+					pr_err("failed to write perf data, error: %m\n");
+				written = 0;
+			}
+			rem_size = cblocks[i]->aio_nbytes - written;
+			if (rem_size == 0) {
+				cblocks[i]->aio_fildes = -1;
+				/* md->refcount is incremented in perf_mmap__push() for
+				 * every enqueued aio write request so decrement it because
+				 * the request is now complete.
+				 */
+				perf_mmap__put(md);
+				if (idx == -1)
+					idx = i;
+			} else {
+				/* aio write request may require restart with the
+				 * reminder if the kernel didn't write whole
+				 * chunk at once.
+				 */
+				rem_off = cblocks[i]->aio_offset + written;
+				rem_buf = (void*)(cblocks[i]->aio_buf + written);
+				record__aio_write(cblocks[i], cblocks[i]->aio_fildes,
+						rem_buf, rem_size, rem_off);
+			}
+		}
+		if (idx == -1)
+			do_suspend = 1;
+	} while (do_suspend);
+
+	return idx;
+}
+
 static int process_synthesized_event(struct perf_tool *tool,
 				     union perf_event *event,
 				     struct perf_sample *sample __maybe_unused,
@@ -130,12 +215,28 @@ static int process_synthesized_event(struct perf_tool *tool,
 	return record__write(rec, event, event->header.size);
 }
 
-static int record__pushfn(void *to, void *bf, size_t size)
+static int record__pushfn(void *to, struct aiocb *cblock, void *data, size_t size)
 {
+	off_t off;
 	struct record *rec = to;
+	int ret, trace_fd = rec->session->data->file.fd;
 
 	rec->samples++;
-	return record__write(rec, bf, size);
+
+	off =
+	lseek(trace_fd, 0, SEEK_CUR);
+	lseek(trace_fd, off + size, SEEK_SET);
+
+	ret = record__aio_write(cblock, trace_fd, data, size, off);
+	if (!ret) {
+		rec->bytes_written += size;
+		if (switch_output_size(rec))
+			trigger_hit(&switch_output_trigger);
+	} else {
+		lseek(trace_fd, off, SEEK_SET);
+	}
+
+	return ret;
 }
 
 static volatile int done;
@@ -511,6 +612,70 @@ static struct perf_event_header finished_round_event = {
 	.type = PERF_RECORD_FINISHED_ROUND,
 };
 
+static void record__aio_complete(struct perf_mmap *md, int i)
+{
+	int aio_errno;
+	void *rem_buf;
+	off_t rem_off;
+	size_t rem_size;
+	ssize_t aio_ret, written;
+	struct aiocb *cblock = md->cblocks[i];
+	struct timespec timeout = { 0, 1000 * 1000  * 1 }; // 1ms
+
+	if (cblock->aio_fildes == -1)
+		return;
+
+	do {
+		if (aio_suspend((const struct aiocb**)&cblock, 1, &timeout)) {
+			if (!(errno == EAGAIN || errno == EINTR))
+				pr_err("failed to sync perf data, error: %m\n");
+			continue;
+		}
+		aio_errno = aio_error(cblock);
+		if (aio_errno == EINPROGRESS)
+			continue;
+		written = aio_ret = aio_return(cblock);
+		if (aio_ret < 0) {
+			if (!(aio_errno == EINTR))
+				pr_err("failed to write perf data, error: %m\n");
+			written = 0;
+		}
+		rem_size = cblock->aio_nbytes - written;
+		if (rem_size == 0) {
+			cblock->aio_fildes = -1;
+			/* md->refcount is incremented in perf_mmap__push() for
+			 * every enqueued aio write request so decrement it because
+			 * the request is now complete.
+			 */
+			perf_mmap__put(md);
+			return;
+		} else {
+			/* aio write request may require restart with the
+			 * reminder if the kernel didn't write whole
+			 * chunk at once.
+			 */
+			rem_off = cblock->aio_offset + written;
+			rem_buf = (void*)(cblock->aio_buf + written);
+			record__aio_write(cblock, cblock->aio_fildes,
+					rem_buf, rem_size, rem_off);
+		}
+	} while (1);
+}
+
+static void record__mmap_read_sync(struct record *rec)
+{
+	int i, j;
+	struct perf_evlist *evlist = rec->evlist;
+	struct perf_mmap *maps = evlist->mmap;
+
+	for (i = 0; i < evlist->nr_mmaps; i++) {
+		struct perf_mmap *map = &maps[i];
+		if (map->base)
+			for (j = 0; j < map->nr_cblocks; ++j)
+				record__aio_complete(map, j);
+	}
+}
+
 static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evlist,
 				    bool overwrite)
 {
@@ -533,7 +698,13 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
 		struct auxtrace_mmap *mm = &maps[i].auxtrace_mmap;
 
 		if (maps[i].base) {
-			if (perf_mmap__push(&maps[i], rec, record__pushfn) != 0) {
+			/* Call record__aio_sync() to allocate free
+			 * map->data buffer or wait till one of the
+			 * buffers becomes available after previous
+			 * aio write request.
+			 */
+			if (perf_mmap__push(&maps[i], rec, record__aio_sync(&maps[i]),
+				record__pushfn) != 0) {
 				rc = -1;
 				goto out;
 			}
@@ -1055,6 +1226,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 			perf_evlist__toggle_bkw_mmap(rec->evlist, BKW_MMAP_DATA_PENDING);
 
 		if (record__mmap_read_all(rec) < 0) {
+			record__mmap_read_sync(rec);
 			trigger_error(&auxtrace_snapshot_trigger);
 			trigger_error(&switch_output_trigger);
 			err = -1;
@@ -1066,6 +1238,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 			if (!trigger_is_error(&auxtrace_snapshot_trigger))
 				record__read_auxtrace_snapshot(rec);
 			if (trigger_is_error(&auxtrace_snapshot_trigger)) {
+				record__mmap_read_sync(rec);
 				pr_err("AUX area tracing snapshot failed\n");
 				err = -1;
 				goto out_child;
@@ -1084,6 +1257,8 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 			 */
 			if (rec->evlist->bkw_mmap_state == BKW_MMAP_RUNNING)
 				continue;
+
+			record__mmap_read_sync(rec);
 			trigger_ready(&switch_output_trigger);
 
 			/*
@@ -1137,6 +1312,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 			disabled = true;
 		}
 	}
+	record__mmap_read_sync(rec);
 	trigger_off(&auxtrace_snapshot_trigger);
 	trigger_off(&switch_output_trigger);
 
diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 384d17cd1379..1d57d8387caf 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -332,12 +332,12 @@ int perf_mmap__read_init(struct perf_mmap *map)
 	return __perf_mmap__read_init(map);
 }
 
-int perf_mmap__push(struct perf_mmap *md, void *to,
-		    int push(void *to, void *buf, size_t size))
+int perf_mmap__push(struct perf_mmap *md, void *to, int idx,
+		    int push(void *to, struct aiocb *cblock, void *data, size_t size))
 {
 	u64 head = perf_mmap__read_head(md);
 	unsigned char *data = md->base + page_size;
-	unsigned long size;
+	unsigned long size, size0 = 0;
 	void *buf;
 	int rc = 0;
 
@@ -345,31 +345,58 @@ int perf_mmap__push(struct perf_mmap *md, void *to,
 	if (rc < 0)
 		return (rc == -EAGAIN) ? 0 : -1;
 
+	/* md->base data is copied into md->data[idx] buffer to
+	 * release space in the kernel buffer as fast as possible,
+	 * thru perf_mmap__consume() below.
+	 *
+	 * That lets the kernel to proceed with storing more
+	 * profiling data into the kernel buffer earlier than other
+	 * per-cpu kernel buffers are handled.
+	 *
+	 * Coping can be done in two steps in case the chunk of
+	 * profiling data crosses the upper bound of the kernel buffer.
+	 * In this case we first move part of data from md->start
+	 * till the upper bound and then the reminder from the
+	 * beginning of the kernel buffer till the end of
+	 * the data chunk.
+	 */
+
 	size = md->end - md->start;
 
 	if ((md->start & md->mask) + size != (md->end & md->mask)) {
 		buf = &data[md->start & md->mask];
-		size = md->mask + 1 - (md->start & md->mask);
-		md->start += size;
-
-		if (push(to, buf, size) < 0) {
-			rc = -1;
-			goto out;
-		}
+		size0 = md->mask + 1 - (md->start & md->mask);
+		md->start += size0;
+		memcpy(md->data[idx], buf, size0);
 	}
 
 	buf = &data[md->start & md->mask];
 	size = md->end - md->start;
 	md->start += size;
+	memcpy(md->data[idx] + size0, buf, size);
 
-	if (push(to, buf, size) < 0) {
-		rc = -1;
-		goto out;
-	}
+	/* Increment md->refcount to guard md->data[idx] buffer
+	 * from premature deallocation because md object can be
+	 * released earlier than aio write request started
+	 * on mmap->data[idx] is complete.
+	 *
+	 * perf_mmap__put() is done at record__aio_sync() or
+	 * record__aio_complete() after started request completion.
+	 */
+
+	perf_mmap__get(md);
 
 	md->prev = head;
 	perf_mmap__consume(md);
-out:
+
+	rc = push(to, md->cblocks[idx], md->data[idx], size0 + size);
+	if (rc) {
+		/* Decrement md->refcount back if aio write
+		 * operation failed to start.
+		 */
+		perf_mmap__put(md);
+	}
+
 	return rc;
 }
 
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index 4a9bb0ecae4f..9a106c075172 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -95,8 +95,8 @@ union perf_event *perf_mmap__read_forward(struct perf_mmap *map);
 
 union perf_event *perf_mmap__read_event(struct perf_mmap *map);
 
-int perf_mmap__push(struct perf_mmap *md, void *to,
-		    int push(void *to, void *buf, size_t size));
+int perf_mmap__push(struct perf_mmap *md, void *to, int aio_idx,
+		    int push(void *to, struct aiocb *cblock, void *data, size_t size));
 
 size_t perf_mmap__mmap_len(struct perf_mmap *map);
 

Re: [PATCH v6 1/2]: perf util: map data buffer for preserving collected data

[Andi Kleen]

>  		.sample		= process_sample_event,
> @@ -1678,6 +1680,8 @@ static struct option __record_options[] = {
>  			  "signal"),
>  	OPT_BOOLEAN(0, "dry-run", &dry_run,
>  		    "Parse options then exit"),
> +	OPT_INTEGER(0, "aio", &record.opts.nr_cblocks,
> +		    "asynchronous trace write operations (min: 1, max: 32, default: 2)"),

would need to be documented in the manpage. But I would rather make it an
~/.perfconfig option


-Andi

Re: [PATCH v6 1/2]: perf util: map data buffer for preserving collected data

[Alexey Budankov]

Hi,

On 04.09.2018 20:34, Andi Kleen wrote:
>>  		.sample		= process_sample_event,
>> @@ -1678,6 +1680,8 @@ static struct option __record_options[] = {
>>  			  "signal"),
>>  	OPT_BOOLEAN(0, "dry-run", &dry_run,
>>  		    "Parse options then exit"),
>> +	OPT_INTEGER(0, "aio", &record.opts.nr_cblocks,
>> +		    "asynchronous trace write operations (min: 1, max: 32, default: 2)"),
> 
> would need to be documented in the manpage. But I would rather make it an
> ~/.perfconfig option

Yep, make sense, it requires to be configurable w/o recompilation and 
at the same time its meaning is not obvious to be on the command line for a user.

> 
> 
> -Andi
>