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authorLinus Torvalds <torvalds@linux-foundation.org>2008-11-13 16:36:30 -0800
committerJunio C Hamano <gitster@pobox.com>2008-11-14 19:11:49 -0800
commit671c9b7e315db89081cc69f83a8f405e4aca37bc (patch)
tree0410fb1af855fc65a7d96dd15410db16e41cbc9f
parenta0d3ab9c277f1a198ec8e29432c0127d4cf719d2 (diff)
downloadgit-671c9b7e315db89081cc69f83a8f405e4aca37bc.tar.gz
git-671c9b7e315db89081cc69f83a8f405e4aca37bc.tar.xz
Add cache preload facility
This can do the lstat() storm in parallel, giving potentially much improved performance for cold-cache cases or things like NFS that have weak metadata caching. Just use "read_cache_preload()" instead of "read_cache()" to force an optimistic preload of the index stat data. The function takes a pathspec as its argument, allowing us to preload only the relevant portion of the index. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--Documentation/config.txt9
-rw-r--r--Makefile1
-rw-r--r--builtin-commit.c8
-rw-r--r--builtin-diff-files.c4
-rw-r--r--builtin-diff.c8
-rw-r--r--cache.h3
-rw-r--r--config.c5
-rw-r--r--environment.c3
-rw-r--r--preload-index.c91
9 files changed, 122 insertions, 10 deletions
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 32dcd643d..0d96e763a 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -413,6 +413,15 @@ data writes properly, but can be useful for filesystems that do not use
journalling (traditional UNIX filesystems) or that only journal metadata
and not file contents (OS X's HFS+, or Linux ext3 with "data=writeback").
+core.preloadindex::
+ Enable parallel index preload for operations like 'git diff'
++
+This can speed up operations like 'git diff' and 'git status' especially
+on filesystems like NFS that have weak caching semantics and thus
+relatively high IO latencies. With this set to 'true', git will do the
+index comparison to the filesystem data in parallel, allowing
+overlapping IO's.
+
alias.*::
Command aliases for the linkgit:git[1] command wrapper - e.g.
after defining "alias.last = cat-file commit HEAD", the invocation
diff --git a/Makefile b/Makefile
index 35adafa01..acac0ae5d 100644
--- a/Makefile
+++ b/Makefile
@@ -496,6 +496,7 @@ LIB_OBJS += write_or_die.o
LIB_OBJS += ws.o
LIB_OBJS += wt-status.o
LIB_OBJS += xdiff-interface.o
+LIB_OBJS += preload-index.o
BUILTIN_OBJS += builtin-add.o
BUILTIN_OBJS += builtin-annotate.o
diff --git a/builtin-commit.c b/builtin-commit.c
index 591d16b91..1677e6b45 100644
--- a/builtin-commit.c
+++ b/builtin-commit.c
@@ -225,18 +225,18 @@ static char *prepare_index(int argc, const char **argv, const char *prefix)
if (interactive) {
interactive_add(argc, argv, prefix);
- if (read_cache() < 0)
+ if (read_cache_preload(NULL) < 0)
die("index file corrupt");
commit_style = COMMIT_AS_IS;
return get_index_file();
}
- if (read_cache() < 0)
- die("index file corrupt");
-
if (*argv)
pathspec = get_pathspec(prefix, argv);
+ if (read_cache_preload(pathspec) < 0)
+ die("index file corrupt");
+
/*
* Non partial, non as-is commit.
*
diff --git a/builtin-diff-files.c b/builtin-diff-files.c
index 2b578c714..5b64011de 100644
--- a/builtin-diff-files.c
+++ b/builtin-diff-files.c
@@ -59,8 +59,8 @@ int cmd_diff_files(int argc, const char **argv, const char *prefix)
(rev.diffopt.output_format & DIFF_FORMAT_PATCH))
rev.combine_merges = rev.dense_combined_merges = 1;
- if (read_cache() < 0) {
- perror("read_cache");
+ if (read_cache_preload(rev.diffopt.paths) < 0) {
+ perror("read_cache_preload");
return -1;
}
result = run_diff_files(&rev, options);
diff --git a/builtin-diff.c b/builtin-diff.c
index 7ceceeb6f..1447c1d6b 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -134,8 +134,8 @@ static int builtin_diff_index(struct rev_info *revs,
revs->max_count != -1 || revs->min_age != -1 ||
revs->max_age != -1)
usage(builtin_diff_usage);
- if (read_cache() < 0) {
- perror("read_cache");
+ if (read_cache_preload(revs->diffopt.paths) < 0) {
+ perror("read_cache_preload");
return -1;
}
return run_diff_index(revs, cached);
@@ -234,8 +234,8 @@ static int builtin_diff_files(struct rev_info *revs, int argc, const char **argv
revs->combine_merges = revs->dense_combined_merges = 1;
setup_work_tree();
- if (read_cache() < 0) {
- perror("read_cache");
+ if (read_cache_preload(revs->diffopt.paths) < 0) {
+ perror("read_cache_preload");
return -1;
}
result = run_diff_files(revs, options);
diff --git a/cache.h b/cache.h
index 3b5f0c4c0..685a8666b 100644
--- a/cache.h
+++ b/cache.h
@@ -262,6 +262,7 @@ static inline void remove_name_hash(struct cache_entry *ce)
#define read_cache() read_index(&the_index)
#define read_cache_from(path) read_index_from(&the_index, (path))
+#define read_cache_preload(pathspec) read_index_preload(&the_index, (pathspec))
#define is_cache_unborn() is_index_unborn(&the_index)
#define read_cache_unmerged() read_index_unmerged(&the_index)
#define write_cache(newfd, cache, entries) write_index(&the_index, (newfd))
@@ -368,6 +369,7 @@ extern int init_db(const char *template_dir, unsigned int flags);
/* Initialize and use the cache information */
extern int read_index(struct index_state *);
+extern int read_index_preload(struct index_state *, const char **pathspec);
extern int read_index_from(struct index_state *, const char *path);
extern int is_index_unborn(struct index_state *);
extern int read_index_unmerged(struct index_state *);
@@ -458,6 +460,7 @@ extern size_t packed_git_limit;
extern size_t delta_base_cache_limit;
extern int auto_crlf;
extern int fsync_object_files;
+extern int core_preload_index;
enum safe_crlf {
SAFE_CRLF_FALSE = 0,
diff --git a/config.c b/config.c
index 67cc1dcad..d2fc8f5f2 100644
--- a/config.c
+++ b/config.c
@@ -490,6 +490,11 @@ static int git_default_core_config(const char *var, const char *value)
return 0;
}
+ if (!strcmp(var, "core.preloadindex")) {
+ core_preload_index = git_config_bool(var, value);
+ return 0;
+ }
+
/* Add other config variables here and to Documentation/config.txt. */
return 0;
}
diff --git a/environment.c b/environment.c
index bb96ac0a7..e278bce0e 100644
--- a/environment.c
+++ b/environment.c
@@ -43,6 +43,9 @@ unsigned whitespace_rule_cfg = WS_DEFAULT_RULE;
enum branch_track git_branch_track = BRANCH_TRACK_REMOTE;
enum rebase_setup_type autorebase = AUTOREBASE_NEVER;
+/* Parallel index stat data preload? */
+int core_preload_index = 0;
+
/* This is set by setup_git_dir_gently() and/or git_default_config() */
char *git_work_tree_cfg;
static char *work_tree;
diff --git a/preload-index.c b/preload-index.c
new file mode 100644
index 000000000..6253578c9
--- /dev/null
+++ b/preload-index.c
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2008 Linus Torvalds
+ */
+#include "cache.h"
+#include <pthread.h>
+
+/*
+ * Mostly randomly chosen maximum thread counts: we
+ * cap the parallelism to 20 threads, and we want
+ * to have at least 500 lstat's per thread for it to
+ * be worth starting a thread.
+ */
+#define MAX_PARALLEL (20)
+#define THREAD_COST (500)
+
+struct thread_data {
+ pthread_t pthread;
+ struct index_state *index;
+ const char **pathspec;
+ int offset, nr;
+};
+
+static void *preload_thread(void *_data)
+{
+ int nr;
+ struct thread_data *p = _data;
+ struct index_state *index = p->index;
+ struct cache_entry **cep = index->cache + p->offset;
+
+ nr = p->nr;
+ if (nr + p->offset > index->cache_nr)
+ nr = index->cache_nr - p->offset;
+
+ do {
+ struct cache_entry *ce = *cep++;
+ struct stat st;
+
+ if (ce_stage(ce))
+ continue;
+ if (ce_uptodate(ce))
+ continue;
+ if (!ce_path_match(ce, p->pathspec))
+ continue;
+ if (lstat(ce->name, &st))
+ continue;
+ if (ie_match_stat(index, ce, &st, 0))
+ continue;
+ ce_mark_uptodate(ce);
+ } while (--nr > 0);
+ return NULL;
+}
+
+static void preload_index(struct index_state *index, const char **pathspec)
+{
+ int threads, i, work, offset;
+ struct thread_data data[MAX_PARALLEL];
+
+ if (!core_preload_index)
+ return;
+
+ threads = index->cache_nr / THREAD_COST;
+ if (threads < 2)
+ return;
+ if (threads > MAX_PARALLEL)
+ threads = MAX_PARALLEL;
+ offset = 0;
+ work = (index->cache_nr + threads - 1) / threads;
+ for (i = 0; i < threads; i++) {
+ struct thread_data *p = data+i;
+ p->index = index;
+ p->pathspec = pathspec;
+ p->offset = offset;
+ p->nr = work;
+ offset += work;
+ if (pthread_create(&p->pthread, NULL, preload_thread, p))
+ die("unable to create threaded lstat");
+ }
+ for (i = 0; i < threads; i++) {
+ struct thread_data *p = data+i;
+ if (pthread_join(p->pthread, NULL))
+ die("unable to join threaded lstat");
+ }
+}
+
+int read_index_preload(struct index_state *index, const char **pathspec)
+{
+ int retval = read_index(index);
+
+ preload_index(index, pathspec);
+ return retval;
+}