From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Opendir(3) and fdopendir(3) are quite expensive system calls when ran in
a loop which iterates all processes in a system times all open files in
each.
Replace some of them (easy ones) with simpler open(2)/read(2) combo to
avoid hammering on the malloc/free.
This brings the default CPU usage of the tool on my desktop from ~3% to
~2%.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
tools/intel_gpu_top.c | 66 +++++++++++++++++++------------------------
1 file changed, 29 insertions(+), 37 deletions(-)
diff --git a/tools/intel_gpu_top.c b/tools/intel_gpu_top.c
index 997aff582ff7..6de8a164fcff 100644
--- a/tools/intel_gpu_top.c
+++ b/tools/intel_gpu_top.c
@@ -1022,12 +1022,12 @@ static void free_clients(struct clients *clients)
free(clients);
}
-static bool is_drm_fd(DIR *fd_dir, const char *name)
+static bool is_drm_fd(int fd_dir, const char *name)
{
struct stat stat;
int ret;
- ret = fstatat(dirfd(fd_dir), name, &stat, 0);
+ ret = fstatat(fd_dir, name, &stat, 0);
return ret == 0 &&
(stat.st_mode & S_IFMT) == S_IFCHR &&
@@ -1054,12 +1054,12 @@ static bool get_task_name(const char *buffer, char *out, unsigned long sz)
return true;
}
-static DIR *opendirat(DIR *at, const char *name)
+static DIR *opendirat(int at, const char *name)
{
DIR *dir;
int fd;
- fd = openat(dirfd(at), name, O_DIRECTORY);
+ fd = openat(at, name, O_DIRECTORY);
if (fd < 0)
return NULL;
@@ -1070,37 +1070,27 @@ static DIR *opendirat(DIR *at, const char *name)
return dir;
}
-static FILE *fropenat(DIR *at, const char *name)
+static size_t readat2buf(int at, const char *name, char *buf, const size_t sz)
{
- FILE *f;
+ ssize_t count;
int fd;
- fd = openat(dirfd(at), name, O_RDONLY);
- if (fd < 0)
- return NULL;
+ fd = openat(at, name, O_RDONLY);
+ if (fd <= 0)
+ return 0;
- f = fdopen(fd, "r");
- if (!f)
- close(fd);
+ count = read(fd, buf, sz - 1);
+ close(fd);
- return f;
-}
+ if (count > 0) {
+ buf[count] = 0;
-static size_t freadat2buf(char *buf, const size_t sz, DIR *at, const char *name)
-{
- size_t count;
- FILE *f;
+ return count;
+ } else {
+ buf[0] = 0;
- f = fropenat(at, name);
- if (!f)
return 0;
-
- buf[sz - 1] = 0;
- count = fread(buf, 1, sz, f);
- buf[count - 1] = 0;
- fclose(f);
-
- return count;
+ }
}
static struct clients *scan_clients(struct clients *clients, bool display)
@@ -1126,10 +1116,11 @@ static struct clients *scan_clients(struct clients *clients, bool display)
return clients;
while ((proc_dent = readdir(proc_dir)) != NULL) {
- DIR *pid_dir = NULL, *fd_dir = NULL, *fdinfo_dir = NULL;
+ int pid_dir = -1, fd_dir = -1;
struct dirent *fdinfo_dent;
char client_name[64] = { };
unsigned int client_pid;
+ DIR *fdinfo_dir = NULL;
char buf[4096];
size_t count;
@@ -1138,11 +1129,12 @@ static struct clients *scan_clients(struct clients *clients, bool display)
if (!isdigit(proc_dent->d_name[0]))
continue;
- pid_dir = opendirat(proc_dir, proc_dent->d_name);
- if (!pid_dir)
+ pid_dir = openat(dirfd(proc_dir), proc_dent->d_name,
+ O_DIRECTORY | O_RDONLY);
+ if (pid_dir < 0)
continue;
- count = freadat2buf(buf, sizeof(buf), pid_dir, "stat");
+ count = readat2buf(pid_dir, "stat", buf, sizeof(buf));
if (!count)
goto next;
@@ -1153,8 +1145,8 @@ static struct clients *scan_clients(struct clients *clients, bool display)
if (!get_task_name(buf, client_name, sizeof(client_name)))
goto next;
- fd_dir = opendirat(pid_dir, "fd");
- if (!fd_dir)
+ fd_dir = openat(pid_dir, "fd", O_DIRECTORY | O_RDONLY);
+ if (fd_dir < 0)
goto next;
fdinfo_dir = opendirat(pid_dir, "fdinfo");
@@ -1196,10 +1188,10 @@ static struct clients *scan_clients(struct clients *clients, bool display)
next:
if (fdinfo_dir)
closedir(fdinfo_dir);
- if (fd_dir)
- closedir(fd_dir);
- if (pid_dir)
- closedir(pid_dir);
+ if (fd_dir >= 0)
+ close(fd_dir);
+ if (pid_dir >= 0)
+ close(pid_dir);
}
closedir(proc_dir);
