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authorArnaldo Carvalho de Melo <acme@redhat.com>2011-01-28 14:49:19 -0200
committerArnaldo Carvalho de Melo <acme@redhat.com>2011-01-29 16:23:58 -0200
commitdc82009aac6ee6e423b48de43a251745c62ab012 (patch)
tree0f3a37aa7340a173f822e60e77e8c8bd5d520a7d /tools/perf
parent54489c189b1a0c10eaf21c6d2c5916b50442c871 (diff)
downloadop-kernel-dev-dc82009aac6ee6e423b48de43a251745c62ab012.zip
op-kernel-dev-dc82009aac6ee6e423b48de43a251745c62ab012.tar.gz
perf record: No need to check for overwrites
As we open the mmap with (PROT_READ | PROT_WRITE), signalling the kernel with perf_mmap__write_tail() when consuming data, so the kernel will not overwrite. Suggested-by: Peter Zijlstra <peterz@infradead.org> 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>
Diffstat (limited to 'tools/perf')
-rw-r--r--tools/perf/builtin-record.c22
1 files changed, 3 insertions, 19 deletions
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d788630..caf9279 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -115,27 +115,11 @@ static void mmap_read(struct perf_mmap *md)
unsigned char *data = md->base + page_size;
unsigned long size;
void *buf;
- 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 < 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)
+ return;
- if (old != head)
- samples++;
+ samples++;
size = head - old;
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