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Commit 82396986 authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf evlist: Refcount mmaps 

We need to know how many fds are using a perf mmap via
PERF_EVENT_IOC_SET_OUTPUT, so that we can know when to ditch an mmap,
refcount it.

v2: Automatically unmap it when the refcount hits one, which will happen
when all fds are filtered by perf_evlist__filter_pollfd(), in later
patches.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20140908153824.GG2773@kernel.org
Link: http://lkml.kernel.org/n/tip-cpv7v2lw0g74ucmxa39xdpms@git.kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 1b85337d

tools/perf/util/evlist.c

+45 −2
Original line number Diff line number Diff line
@@ -28,6 +28,8 @@ 
#define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))

#define SID(e, x, y) xyarray__entry(e->sample_id, x, y)



static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx);



void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus,

		       struct thread_map *threads)

{
@@ -651,14 +653,36 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) 
	return event;

}



static bool perf_mmap__empty(struct perf_mmap *md)

{

	return perf_mmap__read_head(md) != md->prev;

}



static void perf_evlist__mmap_get(struct perf_evlist *evlist, int idx)

{

	++evlist->mmap[idx].refcnt;

}



static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx)

{

	BUG_ON(evlist->mmap[idx].refcnt == 0);



	if (--evlist->mmap[idx].refcnt == 0)

		__perf_evlist__munmap(evlist, idx);

}



void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx)

{

	if (!evlist->overwrite) {

	struct perf_mmap *md = &evlist->mmap[idx];



	if (!evlist->overwrite) {

		unsigned int old = md->prev;



		perf_mmap__write_tail(md, old);

	}



	if (md->refcnt == 1 && perf_mmap__empty(md))

		perf_evlist__mmap_put(evlist, idx);

}



static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx)
@@ -666,6 +690,7 @@ static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx) 
	if (evlist->mmap[idx].base != NULL) {

		munmap(evlist->mmap[idx].base, evlist->mmap_len);

		evlist->mmap[idx].base = NULL;

		evlist->mmap[idx].refcnt = 0;

	}

}
@@ -699,6 +724,20 @@ struct mmap_params { 
static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,

			       struct mmap_params *mp, int fd)

{

	/*

	 * The last one will be done at perf_evlist__mmap_consume(), so that we

	 * make sure we don't prevent tools from consuming every last event in

	 * the ring buffer.

	 *

	 * I.e. we can get the POLLHUP meaning that the fd doesn't exist

	 * anymore, but the last events for it are still in the ring buffer,

	 * waiting to be consumed.

	 *

	 * Tools can chose to ignore this at their own discretion, but the

	 * evlist layer can't just drop it when filtering events in

	 * perf_evlist__filter_pollfd().

	 */

	evlist->mmap[idx].refcnt = 2;

	evlist->mmap[idx].prev = 0;

	evlist->mmap[idx].mask = mp->mask;

	evlist->mmap[idx].base = mmap(NULL, evlist->mmap_len, mp->prot,
@@ -734,10 +773,14 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx, 
		} else {

			if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, *output) != 0)

				return -1;



			perf_evlist__mmap_get(evlist, idx);

		}



		if (perf_evlist__add_pollfd(evlist, fd) < 0)

		if (perf_evlist__add_pollfd(evlist, fd) < 0) {

			perf_evlist__mmap_put(evlist, idx);

			return -1;

		}



		if ((evsel->attr.read_format & PERF_FORMAT_ID) &&

		    perf_evlist__id_add_fd(evlist, evsel, cpu, thread, fd) < 0)

tools/perf/util/evlist.h

+6 −0
Original line number Diff line number Diff line
@@ -18,9 +18,15 @@ struct record_opts; 
#define PERF_EVLIST__HLIST_BITS 8

#define PERF_EVLIST__HLIST_SIZE (1 << PERF_EVLIST__HLIST_BITS)



/**

 * struct perf_mmap - perf's ring buffer mmap details

 *

 * @refcnt - e.g. code using PERF_EVENT_IOC_SET_OUTPUT to share this

 */

struct perf_mmap {

	void		 *base;

	int		 mask;

	int		 refcnt;

	unsigned int	 prev;

	char		 event_copy[PERF_SAMPLE_MAX_SIZE];

};