perf sample: Make user_regs and intr_regs optional

The struct dump_regs contains 512 bytes of cache_regs, meaning the two
values in perf_sample contribute 1088 bytes of its total 1384 bytes
size. Initializing this much memory has a cost reported by Tavian
Barnes <[email protected]> as about 2.5% when running `perf
script --itrace=i0`:
https://lore.kernel.org/lkml/d841b97b3ad2ca8bcab07e4293375fb7c32dfce7.1736618095.git.tavianator@tavianator.com/

Adrian Hunter <[email protected]> replied that the zero
initialization was necessary and couldn't simply be removed.

This patch aims to strike a middle ground of still zeroing the
perf_sample, but removing 79% of its size by make user_regs and
intr_regs optional pointers to zalloc-ed memory. To support the
allocation accessors are created for user_regs and intr_regs. To
support correct cleanup perf_sample__init and perf_sample__exit
functions are created and added throughout the code base.

Signed-off-by: Ian Rogers <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

1 files changed, 9 insertions, 3 deletions

diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index b1abb34d7818..cf6edbe697b2 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -479,19 +479,25 @@ static int process_sample_event(struct machine *machine,
 	struct thread *thread;
 	int ret;
 
-	if (evlist__parse_sample(evlist, event, &sample)) {
+	perf_sample__init(&sample, /*all=*/false);
+	ret = evlist__parse_sample(evlist, event, &sample);
+	if (ret) {
 		pr_debug("evlist__parse_sample failed\n");
-		return -1;
+		ret = -1;
+		goto out;
 	}
 
 	thread = machine__findnew_thread(machine, sample.pid, sample.tid);
 	if (!thread) {
 		pr_debug("machine__findnew_thread failed\n");
-		return -1;
+		ret = -1;
+		goto out;
 	}
 
 	ret = read_object_code(sample.ip, READLEN, sample.cpumode, thread, state);
 	thread__put(thread);
+out:
+	perf_sample__exit(&sample);
 	return ret;
 }