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perf record: Read from backward ring buffer

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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>
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: He Kuang <hekuang@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Wang Nan 2016-05-23 07:13:41 +00:00 committed by Arnaldo Carvalho de Melo
parent 09fa4f4012
commit 3a62a7b820
3 changed files with 54 additions and 0 deletions
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52
tools/perf/builtin-record.c
View file

@ -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;

1
tools/perf/util/evlist.c
View file

@ -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)

1
tools/perf/util/evlist.h
View file

@ -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;