An implementation of stat(2) and lstat(2) caching. Both the return code
and returned information are cached.
Signed-off-by: Luciano Rocha <strange@xxxxxxxxxxxxx>
---
On Sat, Apr 19, 2008 at 03:39:37PM -0700, Linus Torvalds wrote:
> Yeah. I didn't look any further, but we do a total of *nine* 'lstat()'
> calls for each file we know about that is dirty, and *seven* when they are
> clean. Plus maybe a few more.
That's a lot. Why not use a stat cache?
With these changes, my git status . in WebKit changes from 28.215s to
15.414s.
stat-cache.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
stat-cache.h | 9 +++++++
2 files changed, 78 insertions(+), 0 deletions(-)
create mode 100644 stat-cache.c
create mode 100644 stat-cache.h
diff --git a/stat-cache.c b/stat-cache.c
new file mode 100644
index 0000000..6a33cec
--- /dev/null
+++ b/stat-cache.c
@@ -0,0 +1,69 @@
+/*
+ * Cache (l)stat operations
+ */
+
+#include "stat-cache.h"
+#include "hash.h"
+#include "path-list.h";
+
+static struct hash_table stat_cache;
+static struct hash_table lstat_cache;
+
+struct stat_result {
+ struct stat st;
+ int ret;
+};
+
+/* based on hash_name from read_cache.c */
+static unsigned int hash_path(const char *path)
+{
+ unsigned int hash = 0x123;
+
+ while (*path)
+ hash = hash*101 + *path++;
+ return hash;
+}
+
+/* cache is HASH->PATH-LIST->(return code, struct stat) */
+static int cached_stat(int (*f)(const char *, struct stat *),
+ struct hash_table *ht, const char *path, struct stat *buf)
+{
+ unsigned int hash;
+ struct path_list *list;
+ struct path_list_item *cached;
+ struct stat_result *result;
+
+ hash = hash_path(path);
+
+ list = lookup_hash(hash, ht);
+
+ if (!list) {
+ list = xcalloc(1, sizeof *list);
+ list->strdup_paths = 1;
+ insert_hash(hash, list, ht);
+ }
+
+ cached = path_list_lookup(path, list);
+
+ if (cached) {
+ result = cached->util;
+ } else {
+ result = xmalloc(sizeof *result);
+ result->ret = f(path, &result->st);
+ path_list_insert(path, list)->util = result;
+ }
+
+ if (result->ret == 0)
+ memcpy(buf, &result->st, sizeof *buf);
+ return result->ret;
+}
+
+int cstat(const char *path, struct stat *buf)
+{
+ return cached_stat(stat, &stat_cache, path, buf);
+}
+
+int clstat(const char *path, struct stat *buf)
+{
+ return cached_stat(lstat, &lstat_cache, path, buf);
+}
diff --git a/stat-cache.h b/stat-cache.h
new file mode 100644
index 0000000..754348f
--- /dev/null
+++ b/stat-cache.h
@@ -0,0 +1,9 @@
+#ifndef STAT_CACHE_H
+#define STAT_CACHE_H
+
+#include "git-compat-util.h"
+
+int cstat(const char *path, struct stat *buf);
+int clstat(const char *path, struct stat *buf);
+
+#endif /* STAT_CACHE_H */
--
1.5.5.76.gbb45.dirty
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