perf record: Add option to disable collecting build-ids

Collecting build-ids for long running sessions may take a long time
because it needs to traverse the whole just collected perf.data stream
of events, marking the DSOs that had hits and then looking for the
.note.gnu.build-id ELF section.

For things like the 'trace' tool that records and right away consumes
the data on systems where its unlikely that the DSOs being monitored
will change while 'trace' runs, it is desirable to remove build id
collection, so add a -B/--no-buildid option to perf record to allow such
use case.

Longer term we'll avoid all this if we, at DSO load time, in the kernel,
take advantage of this slow code path to collect the build-id and stash
it somewhere, so that we can insert it in the PERF_RECORD_MMAP event.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/tools/perf/util/include/linux/bitops.h b/tools/perf/util/include/linux/bitops.h
index bb4ac2e05385..8be0b968ca0b 100644
--- a/tools/perf/util/include/linux/bitops.h
+++ b/tools/perf/util/include/linux/bitops.h
@@ -13,6 +13,11 @@ static inline void set_bit(int nr, unsigned long *addr)
 	addr[nr / BITS_PER_LONG] |= 1UL << (nr % BITS_PER_LONG);
 }
 
+static inline void clear_bit(int nr, unsigned long *addr)
+{
+	addr[nr / BITS_PER_LONG] &= ~(1UL << (nr % BITS_PER_LONG));
+}
+
 static __always_inline int test_bit(unsigned int nr, const unsigned long *addr)
 {
 	return ((1UL << (nr % BITS_PER_LONG)) &