[tip: perf/core] perf synthetic-events: save 4kb from 2 stack frames

tip-bot2 for Ian Rogers
2020-04-22T12:18:27Z

The following commit has been merged into the perf/core branch of tip:

Commit-ID: 04ed4ccb9c07868bc0cb41f699391332bf62220c
Gitweb: https://git.kernel.org/tip/04ed4ccb9c07868bc0cb41f699391332bf62220c
Author: Ian Rogers <irogers@google.com>
AuthorDate: Thu, 02 Apr 2020 08:43:55 -07:00
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitterDate: Thu, 16 Apr 2020 12:19:13 -03:00

perf synthetic-events: save 4kb from 2 stack frames

Reuse an existing char buffer to avoid two PATH_MAX sized char buffers.

Reduces stack frame sizes by 4kb.

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'.

The performance impact of this change is negligible.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrey Zhizhikin <andrey.z@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200402154357.107873-4-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/synthetic-events.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index a661b12..9d4aa95 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -71,7 +71,6 @@ 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;
@@ -81,11 +80,11 @@ 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);
+ snprintf(bf, sizeof(bf), "/proc/%d/status", pid);

- fd = open(filename, O_RDONLY);
+ fd = open(bf, O_RDONLY);
if (fd < 0) {
- pr_debug("couldn't open %s\n", filename);
+ pr_debug("couldn't open %s\n", bf);
return -1;
}

@@ -281,9 +280,9 @@ 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;
+ char bf[BUFSIZ];
bool truncation = false;
unsigned long long timeout = proc_map_timeout * 1000000ULL;
int rc = 0;
@@ -293,15 +292,15 @@ 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);
+ snprintf(bf, sizeof(bf), "%s/proc/%d/task/%d/maps",
+ machine->root_dir, pid, pid);

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

@@ -309,7 +308,6 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
t = rdclock();

while (1) {
- char bf[BUFSIZ];
char prot[5];
char execname[PATH_MAX];
char anonstr[] = "//anon";
@@ -321,10 +319,10 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
break;

if ((rdclock() - t) > timeout) {
- pr_warning("Reading %s time out. "
+ pr_warning("Reading %s/proc/%d/task/%d/maps 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;
}