[pacman-dev] [PATCH] Avoid stat call to determine is_directory if possible
Dan McGee
dan at archlinux.org
Tue Oct 5 12:49:48 EDT 2010
On Linux and OS X, we can determine if an entry obtained through a readdir()
call is a directory without also having to stat it. This can save a
significant number of syscalls; it does make the getdents() call more
expensive but cuts out a lot of stat() calls.
Before:
$ strace -c pacman -Ss pacman
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
82.95 0.016153 1 21733 read
4.21 0.000819 0 11056 23 open
3.96 0.000771 0 17602 1 access
1.84 0.000358 0 11026 fstat
1.72 0.000334 0 11033 close
1.54 0.000299 0 6608 3 stat
0.00 0.000000 0 20 getdents
------ ----------- ----------- --------- --------- ----------------
100.00 0.019473 101271 28 total
After:
$ strace -c ./src/pacman/.libs/lt-pacman -Ss pacman
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
30.11 0.001503 75 20 getdents
14.81 0.000739 0 21733 read
13.91 0.000694 0 17602 1 access
13.32 0.000665 0 11072 39 open
6.61 0.000330 0 11026 fstat
6.03 0.000301 0 11033 close
0.00 0.000000 0 9 6 stat
------ ----------- ----------- --------- --------- ----------------
100.00 0.004991 94686 47 total
Obviously the numbers will show some variation, but it never seems to be
slower so this should be a win overall.
Signed-off-by: Dan McGee <dan at archlinux.org>
---
List,
My take on a rather stale patch in my inbox. I added the is_dir() static
function so we can still run on platforms not supporting this shortcut, and I
also wasn't sure why the access() call was removed in the orignal patch (commit
messages explaining changes, anyone?). Let me know what you think.
-Dan
-Dan
lib/libalpm/be_files.c | 29 +++++++++++++++++++----------
1 files changed, 19 insertions(+), 10 deletions(-)
diff --git a/lib/libalpm/be_files.c b/lib/libalpm/be_files.c
index 4432171..0f055e0 100644
--- a/lib/libalpm/be_files.c
+++ b/lib/libalpm/be_files.c
@@ -108,13 +108,28 @@ static int dirlist_from_tar(const char *archive, alpm_list_t **dirlist)
return(0);
}
+static int is_dir(const char *path, struct dirent *entry)
+{
+#ifdef DT_DIR
+ return(entry->d_type == DT_DIR);
+#else
+ char buffer[PATH_MAX];
+ snprintf(buffer, PATH_MAX, "%s/%s", path, entry->d_name);
+
+ struct stat sbuf;
+ if (!stat(buffer, &sbuf)) {
+ return(S_ISDIR(sbuf.st_mode));
+ }
+
+ return(0);
+#endif
+}
+
/* create list of directories in db */
static int dirlist_from_fs(const char *syncdbpath, alpm_list_t **dirlist)
{
DIR *dbdir;
struct dirent *ent = NULL;
- struct stat sbuf;
- char path[PATH_MAX];
dbdir = opendir(syncdbpath);
if (dbdir != NULL) {
@@ -127,9 +142,7 @@ static int dirlist_from_fs(const char *syncdbpath, alpm_list_t **dirlist)
continue;
}
- /* stat the entry, make sure it's a directory */
- snprintf(path, PATH_MAX, "%s%s", syncdbpath, name);
- if(stat(path, &sbuf) != 0 || !S_ISDIR(sbuf.st_mode)) {
+ if(!is_dir(syncdbpath, ent)) {
continue;
}
@@ -353,8 +366,6 @@ int _alpm_db_populate(pmdb_t *db)
{
int count = 0;
struct dirent *ent = NULL;
- struct stat sbuf;
- char path[PATH_MAX];
const char *dbpath;
DIR *dbdir;
@@ -374,9 +385,7 @@ int _alpm_db_populate(pmdb_t *db)
if(strcmp(name, ".") == 0 || strcmp(name, "..") == 0) {
continue;
}
- /* stat the entry, make sure it's a directory */
- snprintf(path, PATH_MAX, "%s%s", dbpath, name);
- if(stat(path, &sbuf) != 0 || !S_ISDIR(sbuf.st_mode)) {
+ if(!is_dir(dbpath, ent)) {
continue;
}
--
1.7.3.1
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