Messages in this thread Patch in this message | | | From | Wang Nan <> | Subject | [PATCH 15/17] perf record: Read from backward ring buffer | Date | Fri, 13 May 2016 07:56:12 +0000 |
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Introduce rb_find_range() to find start and end position from a backward ring buffer.
Signed-off-by: Wang Nan <wangnan0@huawei.com> Signed-off-by: He Kuang <hekuang@huawei.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.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 --- tools/perf/builtin-record.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 9f4d3ad..e637ea2 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -83,6 +83,61 @@ 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, int idx, + void *data, int mask, u64 head, u64 old, + u64 *start, u64 *end) +{ + int channel; + + channel = perf_evlist__idx_channel(evlist, idx); + if (!perf_evlist__channel_check(evlist, channel, RDONLY)) { + *start = old; + *end = head; + return 0; + } + + if (perf_evlist__channel_check(evlist, channel, BACKWARD)) + return backward_rb_find_range(data, mask, head, start, end); + + WARN_ONCE(1, "Unable to find start position from a read-only ring buffer\n"); + return -1; +} + static int record__mmap_read(struct record *rec, int idx) { struct perf_mmap *md = &rec->evlist->mmap[idx]; @@ -94,6 +149,10 @@ static int record__mmap_read(struct record *rec, int idx) void *buf; int rc = 0; + if (rb_find_range(rec->evlist, idx, data, md->mask, head, + old, &start, &end)) + return -1; + if (start == end) return 0; -- 1.8.3.4
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