From dc82009aac6ee6e423b48de43a251745c62ab012 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Fri, 28 Jan 2011 14:49:19 -0200 Subject: [PATCH] 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 Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Mike Galbraith Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Tom Zanussi LKML-Reference: Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 22 +++------------------- 1 file changed, 3 insertions(+), 19 deletions(-) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index d7886307f6f4..caf927978d92 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; -- 2.20.1