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Commit 3a62a7b8 authored by Wang Nan's avatar Wang Nan Committed by Arnaldo Carvalho de Melo
Browse files

perf record: Read from backward ring buffer 



Introduce rb_find_range() to find start and end position from a backward
ring buffer.

Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1463987628-163563-5-git-send-email-wangnan0@huawei.com


Signed-off-by: default avatarHe Kuang <hekuang@huawei.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 09fa4f40

tools/perf/builtin-record.c

+52 −0
Original line number Diff line number Diff line
@@ -83,6 +83,54 @@ static int process_synthesized_event(struct perf_tool *tool, 
	return record__write(rec, event, event->header.size);

}



static int

backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)

{

	struct perf_event_header *pheader;

	u64 evt_head = head;

	int size = mask + 1;



	pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);

	pheader = (struct perf_event_header *)(buf + (head & mask));

	*start = head;

	while (true) {

		if (evt_head - head >= (unsigned int)size) {

			pr_debug("Finshed reading backward ring buffer: rewind\n");

			if (evt_head - head > (unsigned int)size)

				evt_head -= pheader->size;

			*end = evt_head;

			return 0;

		}



		pheader = (struct perf_event_header *)(buf + (evt_head & mask));



		if (pheader->size == 0) {

			pr_debug("Finshed reading backward ring buffer: get start\n");

			*end = evt_head;

			return 0;

		}



		evt_head += pheader->size;

		pr_debug3("move evt_head: %"PRIx64"\n", evt_head);

	}

	WARN_ONCE(1, "Shouldn't get here\n");

	return -1;

}



static int

rb_find_range(struct perf_evlist *evlist,

	      void *data, int mask, u64 head, u64 old,

	      u64 *start, u64 *end)

{

	if (!evlist->backward) {

		*start = old;

		*end = head;

		return 0;

	}



	return backward_rb_find_range(data, mask, head, start, end);

}



static int record__mmap_read(struct record *rec, int idx)

{

	struct perf_mmap *md = &rec->evlist->mmap[idx];
@@ -94,6 +142,10 @@ static int record__mmap_read(struct record *rec, int idx) 
	void *buf;

	int rc = 0;



	if (rb_find_range(rec->evlist, data, md->mask, head,

			  old, &start, &end))

		return -1;



	if (start == end)

		return 0;

tools/perf/util/evlist.c

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus, 
	perf_evlist__set_maps(evlist, cpus, threads);

	fdarray__init(&evlist->pollfd, 64);

	evlist->workload.pid = -1;

	evlist->backward = false;

}



struct perf_evlist *perf_evlist__new(void)

tools/perf/util/evlist.h

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ struct perf_evlist { 
	bool		 overwrite;

	bool		 enabled;

	bool		 has_user_cpus;

	bool		 backward;

	size_t		 mmap_len;

	int		 id_pos;

	int		 is_pos;