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Commit 7bb41152 authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf evlist: Support non overwrite mode in perf_evlist__read_on_cpu 



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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent ef2bf6d0

tools/perf/util/evlist.c

+20 −15
Original line number Diff line number Diff line
@@ -116,8 +116,8 @@ 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 (evlist->overwrite) {

		/*

		 * 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.
@@ -126,7 +126,7 @@ event_t *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu) 
		 *

		 * In either case, truncate and restart at head.

		 */

	diff = head - old;

		int diff = head - old;

		if (diff > md->mask / 2 || diff < 0) {

			fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
@@ -135,6 +135,7 @@ event_t *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu) 
			 */

			old = head;

		}

	}



	if (old != head) {

		size_t size;
@@ -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;

}

tools/perf/util/evlist.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

tools/perf/util/evsel.c

+1 −0
Original line number Diff line number Diff line
@@ -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);