Messages in this thread Patch in this message | | | From | Arnaldo Carvalho de Melo <> | Subject | [PATCH 1/7] perf record: No need to check for overwrites | Date | Sat, 29 Jan 2011 20:19:13 -0200 |
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From: Arnaldo Carvalho de Melo <acme@redhat.com>
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> --- 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; -- 1.6.2.5
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