Em Tue, Nov 24, 2015 at 08:24:07AM -0700, David Ahern escreveu:
> On 11/24/15 8:20 AM, Arnaldo Carvalho de Melo wrote:
> >Em Tue, Nov 24, 2015 at 08:06:41AM -0700, David Ahern escreveu:
> >>On 11/24/15 7:00 AM, Yunlong Song wrote:
> >>>+static int record__write(struct record *rec, void *bf, size_t size)
> >>>+{
> >>>+ if (rec->memory.size && memory_enabled) {
> >>>+ if (perf_memory__write(&rec->memory, bf, size) < 0) {
> >>>+ pr_err("failed to write memory data, error: %m\n");
> >>>+ return -1;
> >>>+ }
> >>>+ } else {
> >>>+ if (perf_data_file__write(rec->session->file, bf, size) < 0) {
> >>>+ pr_err("failed to write perf data, error: %m\n");
> >>>+ return -1;
> >>>+ }
> >>>+ rec->bytes_written += size;
> >>> }
> >>>
> >>>- rec->bytes_written += size;
> >>> return 0;
> >>> }
> >>>
> >>>@@ -86,6 +214,8 @@ static int record__mmap_read(struct record *rec, int
> >>>idx)
> >>> if (old == head)
> >>> return 0;
> >>>
> >>>+ memory_enabled = 1;
> >>>+
> >>> rec->samples++;
> >>>
> >>> size = head - old;
> >>>@@ -113,6 +243,7 @@ static int record__mmap_read(struct record *rec, int
> >>>idx)
> >>> md->prev = old;
> >>> perf_evlist__mmap_consume(rec->evlist, idx);
> >>> out:
> >>>+ memory_enabled = 0;
> >>> return rc;
> >>> }
> >>>
> >>
> >>So you are basically ignoring all samples until SIGUSR2 is received. That
> >
> >No, he is not, its just that his code is difficult to follow, has to be
> >rewritten, but he is ignoring just PERF_RECORD_SAMPLE events, so it
> >will..
> >>means the resulting data file will have limited history of task events for
> >... have a complete history of task events, since PERF_RECORD_FORK, etc
> >are not being ignored.
> >No?
> perf-record does not process events, it only writes to a file. If that is
> skipped then it skips all events regardless of type.
perf-record without his patch? yes, but with his patch it does:
__cmd_record()
for (;;)
record__mmap_read_all()
record__write()
perf_memory__write()
event = (union perf_event *)(memory->start +
memory->head + skip);
if (event->header.type != PERF_RECORD_SAMPLE) {
if (buf_to_file(rec, memory->start, memory->size,
}
I almost thought that I had been fooled by the difficulty to follow his
patch and was forgetting that 'perf record' doesn't processes events,
and hasn't done so for a very good reason: to reduce its impact on the
observed workload, but that ain't so, no?
So, when not snapshotting, what you said remains true:
static int record__write(struct record *rec, void *bf, size_t size)
{
if (rec->memory.size && memory_enabled) {
if (perf_memory__write(&rec->memory, bf, size) < 0) {
pr_err("failed to write memory data, error: %m\n");
return -1;
}
} else {
if (perf_data_file__write(rec->session->file, bf, size) < 0) {
I'll continue taking the else branch and in that case, no events are
processed, we just dump that bf into the rec->session->file and go on
with life.
- Arnaldo
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