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Subject[PATCH 12/14] perf evlist: Refcount mmaps
Date
From: Arnaldo Carvalho de Melo <acme@redhat.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.

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-9ymfcxmk52sb7u1g0i3aiovh@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/evlist.c | 21 ++++++++++++++++++++-
tools/perf/util/evlist.h | 6 ++++++
2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 477ede5367ee..662057a44126 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -664,6 +664,7 @@ 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].nfds = 0;
}
}

@@ -697,6 +698,7 @@ struct mmap_params {
static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
struct mmap_params *mp, int fd)
{
+ evlist->mmap[idx].nfds = 1;
evlist->mmap[idx].prev = 0;
evlist->mmap[idx].mask = mp->mask;
evlist->mmap[idx].base = mmap(NULL, evlist->mmap_len, mp->prot,
@@ -711,6 +713,19 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
return 0;
}

+static void perf_evlist__mmap_get(struct perf_evlist *evlist, int idx)
+{
+ ++evlist->mmap[idx].nfds;
+}
+
+static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx)
+{
+ BUG_ON(evlist->mmap[idx].nfds == 0);
+
+ if (--evlist->mmap[idx].nfds == 0)
+ __perf_evlist__munmap(evlist, idx);
+}
+
static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
struct mmap_params *mp, int cpu,
int thread, int *output)
@@ -732,10 +747,14 @@ 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..19bbe0410827 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
+ *
+ * @nfds - file descriptors pointing here via PERF_EVENT_IOC_SET_OUTPUT
+ */
struct perf_mmap {
void *base;
int mask;
+ int nfds;
unsigned int prev;
char event_copy[PERF_SAMPLE_MAX_SIZE];
};
--
1.9.3


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