Commit-ID: dc82009aac6ee6e423b48de43a251745c62ab012
Gitweb: http://git.kernel.org/tip/dc82009aac6ee6e423b48de43a251745c62ab012
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Fri, 28 Jan 2011 14:49:19 -0200
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Sat, 29 Jan 2011 16:23:58 -0200
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@xxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Tom Zanussi <tzanussi@xxxxxxxxx>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/builtin-record.c | 24 ++++--------------------
1 files changed, 4 insertions(+), 20 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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