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Subject[PATCH] perf synthetic-events: save 4kb from 2 stack frames
From
Reduce the scope of PATH_MAX sized char buffers so that the compiler can
overlap their usage.

perf_event__synthesize_mmap_events before 'sub $0x45b8,%rsp' after
'sub $0x35b8,%rsp'.

perf_event__get_comm_ids before 'sub $0x2028,%rsp' after 'sub $0x1028,%rsp'.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/synthetic-events.c | 46 ++++++++++++++++++------------
1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 3f28af39f9c6..9ff54707bb30 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -70,7 +70,6 @@ int perf_tool__process_synth_event(struct perf_tool *tool,
static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len,
pid_t *tgid, pid_t *ppid)
{
- char filename[PATH_MAX];
char bf[4096];
int fd;
size_t size = 0;
@@ -80,12 +79,16 @@ static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len,
*tgid = -1;
*ppid = -1;

- snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
+ {
+ char filename[PATH_MAX];

- fd = open(filename, O_RDONLY);
- if (fd < 0) {
- pr_debug("couldn't open %s\n", filename);
- return -1;
+ snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
+
+ fd = open(filename, O_RDONLY);
+ if (fd < 0) {
+ pr_debug("couldn't open %s\n", filename);
+ return -1;
+ }
}

n = read(fd, bf, sizeof(bf) - 1);
@@ -280,7 +283,6 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
struct machine *machine,
bool mmap_data)
{
- char filename[PATH_MAX];
FILE *fp;
unsigned long long t;
bool truncation = false;
@@ -292,18 +294,22 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
if (machine__is_default_guest(machine))
return 0;

- snprintf(filename, sizeof(filename), "%s/proc/%d/task/%d/maps",
- machine->root_dir, pid, pid);
+#define FILENAME_FMT_STRING "%s/proc/%d/task/%d/maps"
+ {
+ char filename[PATH_MAX];

- fp = fopen(filename, "r");
- if (fp == NULL) {
- /*
- * We raced with a task exiting - just return:
- */
- pr_debug("couldn't open %s\n", filename);
- return -1;
- }
+ snprintf(filename, sizeof(filename), FILENAME_FMT_STRING,
+ machine->root_dir, pid, pid);

+ fp = fopen(filename, "r");
+ if (fp == NULL) {
+ /*
+ * We raced with a task exiting - just return:
+ */
+ pr_debug("couldn't open %s\n", filename);
+ return -1;
+ }
+ }
event->header.type = PERF_RECORD_MMAP2;
t = rdclock();

@@ -320,10 +326,10 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
break;

if ((rdclock() - t) > timeout) {
- pr_warning("Reading %s time out. "
+ pr_warning("Reading " FILENAME_FMT_STRING " time out. "
"You may want to increase "
"the time limit by --proc-map-timeout\n",
- filename);
+ machine->root_dir, pid, pid);
truncation = true;
goto out;
}
@@ -412,6 +418,8 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,

fclose(fp);
return rc;
+
+#undef FILENAME_FMT_STRING
}

int perf_event__synthesize_modules(struct perf_tool *tool, perf_event__handler_t process,
--
2.25.1.696.g5e7596f4ac-goog
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