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perf evlist: Support non overwrite mode in perf_evlist__read_on_cpu

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I.e. stash the overwrite mode in struct perf_evlist and act accordingly
in perf_evlist__read_on_cpu, not checking for overwrites and touching
the tail after consuming one event, like perf record does, for instance.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2011-01-29 09:08:13 -02:00
parent ef2bf6d043
commit 7bb41152b9
3 changed files with 22 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
tools/perf/util/evlist.c
View File

@ -116,24 +116,25 @@ event_t *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu)
unsigned int old = md->prev;
unsigned char *data = md->base + page_size;
event_t *event = NULL;
int diff;
/*
* If we're further behind than half the buffer, there's a chance
* the writer will bite our tail and mess up the samples under us.
*
* If we somehow ended up ahead of the head, we got messed up.
*
* In either case, truncate and restart at head.
*/
diff = head - old;
if (diff > md->mask / 2 || diff < 0) {
fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
if (evlist->overwrite) {
/*
* head points to a known good entry, start there.
* If we're further behind than half the buffer, there's a chance
* the writer will bite our tail and mess up the samples under us.
*
* If we somehow ended up ahead of the head, we got messed up.
*
* In either case, truncate and restart at head.
*/
old = head;
int diff = head - old;
if (diff > md->mask / 2 || diff < 0) {
fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
/*
* head points to a known good entry, start there.
*/
old = head;
}
}
if (old != head) {
@ -166,5 +167,9 @@ event_t *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu)
}
md->prev = old;
if (!evlist->overwrite)
perf_mmap__write_tail(md, old);
return event;
}

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

@ -16,6 +16,7 @@ struct perf_evlist {
int nr_entries;
int nr_fds;
int mmap_len;
bool overwrite;
event_t event_copy;
struct perf_mmap *mmap;
struct pollfd *pollfd;

1
tools/perf/util/evsel.c
View File

@ -327,6 +327,7 @@ int perf_evlist__mmap(struct perf_evlist *evlist, struct cpu_map *cpus,
perf_evlist__alloc_pollfd(evlist, cpus->nr, threads->nr) < 0)
return -ENOMEM;
evlist->overwrite = overwrite;
evlist->mmap_len = (pages + 1) * page_size;
first_evsel = list_entry(evlist->entries.next, struct perf_evsel, node);