From: Kan Liang <[email protected]> The perf record has specific codes to calculate the ringbuffer position for both overwrite and non-overwrite mode. Now, only perf record supports both modes. The perf top will support both modes later. It is useful to make the specific codes generic.
Introduce a new interface perf_mmap__read_init() to find ringbuffer position. The perf_mmap__read_init() is actually factored out from perf_mmap__push(). There are slight differences. - Add a check for map->refcnt - Add new return value logic, EAGAIN and EINVAL. Signed-off-by: Kan Liang <[email protected]> --- tools/perf/util/mmap.c | 43 +++++++++++++++++++++++++++++++++++++++++++ tools/perf/util/mmap.h | 2 ++ 2 files changed, 45 insertions(+) diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c index 05076e6..414089f 100644 --- a/tools/perf/util/mmap.c +++ b/tools/perf/util/mmap.c @@ -267,6 +267,49 @@ static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u6 return -1; } +/* + * Report the start and end of the available data in ringbuffer + */ +int perf_mmap__read_init(struct perf_mmap *map, bool overwrite, + u64 *startp, u64 *endp) +{ + unsigned char *data = map->base + page_size; + u64 head = perf_mmap__read_head(map); + u64 old = map->prev; + unsigned long size; + + /* + * Check if event was unmapped due to a POLLHUP/POLLERR. + */ + if (!refcount_read(&map->refcnt)) + return -EINVAL; + + *startp = overwrite ? head : old; + *endp = overwrite ? old : head; + + if (*startp == *endp) + return -EAGAIN; + + size = *endp - *startp; + if (size > (unsigned long)(map->mask) + 1) { + if (!overwrite) { + WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n"); + + map->prev = head; + perf_mmap__consume(map, overwrite); + return -EAGAIN; + } + + /* + * Backward ring buffer is full. We still have a chance to read + * most of data from it. + */ + if (overwrite_rb_find_range(data, map->mask, head, startp, endp)) + return -EINVAL; + } + return 0; +} + int perf_mmap__push(struct perf_mmap *md, bool overwrite, void *to, int push(void *to, void *buf, size_t size)) { diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h index e43d7b5..0633308 100644 --- a/tools/perf/util/mmap.h +++ b/tools/perf/util/mmap.h @@ -94,4 +94,6 @@ int perf_mmap__push(struct perf_mmap *md, bool backward, size_t perf_mmap__mmap_len(struct perf_mmap *map); +int perf_mmap__read_init(struct perf_mmap *map, bool overwrite, + u64 *startp, u64 *endp); #endif /*__PERF_MMAP_H */ -- 2.5.5
