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Date: Thu, 25 Sep 2014 18:57:47 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Borislav Petkov <bp@...e.de>,
Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
David Ahern <dsahern@...il.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Jean Pihet <jean.pihet@...aro.org>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Paul Mackerras <paulus@...ba.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [PATCH 10/14] perf evlist: Refcount mmaps
From: Arnaldo Carvalho de Melo <acme@...hat.com>
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@...el.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Jean Pihet <jean.pihet@...aro.org>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.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: Arnaldo Carvalho de Melo <acme@...hat.com>
---
tools/perf/util/evlist.c | 47 +++++++++++++++++++++++++++++++++++++++++++++--
tools/perf/util/evlist.h | 6 ++++++
2 files changed, 51 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 398dab1a08cc..efddee5a23e9 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -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)
{
+ struct perf_mmap *md = &evlist->mmap[idx];
+
if (!evlist->overwrite) {
- struct perf_mmap *md = &evlist->mmap[idx];
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)
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index fc013704d903..bd312b01e876 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -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];
};
--
1.9.3
--
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