If you have a large work tree but only make changes in a subset, then
$GIT_DIR/index's size should be stable after a while. If you change
branches that touch something else, $GIT_DIR/index's size may grow
large that it becomes as slow as the unified index. Do --split-index
again occasionally to force all changes back to the shared index and
keep $GIT_DIR/index small.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
---
Documentation/git-update-index.txt | 11 +++++++
builtin/update-index.c | 18 ++++++++++
cache.h | 1 +
read-cache.c | 67 ++++++++++++++++++++++++++++++++++----
split-index.c | 23 +++++++++++++
5 files changed, 114 insertions(+), 6 deletions(-)
diff --git a/Documentation/git-update-index.txt b/Documentation/git-update-index.txt
index d6de4a0..dfc09d9 100644
--- a/Documentation/git-update-index.txt
+++ b/Documentation/git-update-index.txt
@@ -161,6 +161,17 @@ may not support it yet.
Only meaningful with `--stdin` or `--index-info`; paths are
separated with NUL character instead of LF.
+--split-index::
+--no-split-index::
+ Enable or disable split index mode. If enabled, the index is
+ split into two files, $GIT_DIR/index and $GIT_DIR/sharedindex.<SHA-1>.
+ Changes are accumulated in $GIT_DIR/index while the shared
+ index file contains all index entries stays unchanged. If
+ split-index mode is already enabled and `--split-index` is
+ given again, all changes in $GIT_DIR/index are pushed back to
+ the shared index file. This mode is designed for very large
+ indexes that take a signficant amount of time to read or write.
+
\--::
Do not interpret any more arguments as options.
diff --git a/builtin/update-index.c b/builtin/update-index.c
index f7a19c4..b0503f4 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -13,6 +13,7 @@
#include "parse-options.h"
#include "pathspec.h"
#include "dir.h"
+#include "split-index.h"
/*
* Default to not allowing changes to the list of files. The
@@ -742,6 +743,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
char set_executable_bit = 0;
struct refresh_params refresh_args = {0, &has_errors};
int lock_error = 0;
+ int split_index = -1;
struct lock_file *lock_file;
struct parse_opt_ctx_t ctx;
int parseopt_state = PARSE_OPT_UNKNOWN;
@@ -824,6 +826,8 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
resolve_undo_clear_callback},
OPT_INTEGER(0, "index-version", &preferred_index_format,
N_("write index in this format")),
+ OPT_BOOL(0, "split-index", &split_index,
+ N_("enable or disable split index")),
OPT_END()
};
@@ -917,6 +921,20 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
strbuf_release(&buf);
}
+ if (split_index > 0) {
+ init_split_index(&the_index);
+ the_index.cache_changed |= SPLIT_INDEX_ORDERED;
+ } else if (!split_index && the_index.split_index) {
+ /*
+ * can't discard_split_index(&the_index); because that
+ * will destroy split_index->base->cache[], which may
+ * be shared with the_index.cache[]. So yeah we're
+ * leaking a bit here.
+ */
+ the_index.split_index = NULL;
+ the_index.cache_changed |= SOMETHING_CHANGED;
+ }
+
if (active_cache_changed) {
if (newfd < 0) {
if (refresh_args.flags & REFRESH_QUIET)
diff --git a/cache.h b/cache.h
index ddb7cd2..7523c28 100644
--- a/cache.h
+++ b/cache.h
@@ -278,6 +278,7 @@ static inline unsigned int canon_mode(unsigned int mode)
#define CE_ENTRY_ADDED (1 << 3)
#define RESOLVE_UNDO_CHANGED (1 << 4)
#define CACHE_TREE_CHANGED (1 << 5)
+#define SPLIT_INDEX_ORDERED (1 << 6)
struct split_index;
struct index_state {
diff --git a/read-cache.c b/read-cache.c
index af475dc..8ecb959 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -15,6 +15,7 @@
#include "strbuf.h"
#include "varint.h"
#include "split-index.h"
+#include "sigchain.h"
static struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
unsigned int options);
@@ -39,7 +40,8 @@ static struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
/* changes that can be kept in $GIT_DIR/index (basically all extensions) */
#define EXTMASK (RESOLVE_UNDO_CHANGED | CACHE_TREE_CHANGED | \
- CE_ENTRY_ADDED | CE_ENTRY_REMOVED | CE_ENTRY_CHANGED)
+ CE_ENTRY_ADDED | CE_ENTRY_REMOVED | CE_ENTRY_CHANGED | \
+ SPLIT_INDEX_ORDERED)
struct index_state the_index;
static const char *alternate_index_output;
@@ -1860,7 +1862,8 @@ void update_index_if_able(struct index_state *istate, struct lock_file *lockfile
rollback_lock_file(lockfile);
}
-static int do_write_index(struct index_state *istate, int newfd)
+static int do_write_index(struct index_state *istate, int newfd,
+ int strip_extensions)
{
git_SHA_CTX c;
struct cache_header hdr;
@@ -1923,7 +1926,7 @@ static int do_write_index(struct index_state *istate, int newfd)
strbuf_release(&previous_name_buf);
/* Write extension data here */
- if (istate->split_index) {
+ if (!strip_extensions && istate->split_index) {
struct strbuf sb = STRBUF_INIT;
err = write_link_extension(&sb, istate) < 0 ||
@@ -1934,7 +1937,7 @@ static int do_write_index(struct index_state *istate, int newfd)
if (err)
return -1;
}
- if (istate->cache_tree) {
+ if (!strip_extensions && istate->cache_tree) {
struct strbuf sb = STRBUF_INIT;
cache_tree_write(&sb, istate->cache_tree);
@@ -1944,7 +1947,7 @@ static int do_write_index(struct index_state *istate, int newfd)
if (err)
return -1;
}
- if (istate->resolve_undo) {
+ if (!strip_extensions && istate->resolve_undo) {
struct strbuf sb = STRBUF_INIT;
resolve_undo_write(&sb, istate->resolve_undo);
@@ -1985,7 +1988,7 @@ static int commit_locked_index(struct lock_file *lk)
static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,
unsigned flags)
{
- int ret = do_write_index(istate, lock->fd);
+ int ret = do_write_index(istate, lock->fd, 0);
if (ret)
return ret;
assert((flags & (COMMIT_LOCK | CLOSE_LOCK)) !=
@@ -2009,6 +2012,52 @@ static int write_split_index(struct index_state *istate,
return ret;
}
+static char *temporary_sharedindex;
+
+static void remove_temporary_sharedindex(void)
+{
+ if (temporary_sharedindex) {
+ unlink_or_warn(temporary_sharedindex);
+ free(temporary_sharedindex);
+ temporary_sharedindex = NULL;
+ }
+}
+
+static void remove_temporary_sharedindex_on_signal(int signo)
+{
+ remove_temporary_sharedindex();
+ sigchain_pop(signo);
+ raise(signo);
+}
+
+static int write_shared_index(struct index_state *istate)
+{
+ struct split_index *si = istate->split_index;
+ static int installed_handler;
+ int fd, ret;
+
+ temporary_sharedindex = git_pathdup("sharedindex_XXXXXX");
+ fd = xmkstemp(temporary_sharedindex);
+ if (!installed_handler) {
+ atexit(remove_temporary_sharedindex);
+ sigchain_push_common(remove_temporary_sharedindex_on_signal);
+ }
+ move_cache_to_base_index(istate);
+ ret = do_write_index(si->base, fd, 1);
+ close(fd);
+ if (ret) {
+ remove_temporary_sharedindex();
+ return ret;
+ }
+ ret = rename(temporary_sharedindex,
+ git_path("sharedindex.%s", sha1_to_hex(si->base->sha1)));
+ free(temporary_sharedindex);
+ temporary_sharedindex = NULL;
+ if (!ret)
+ hashcpy(si->base_sha1, si->base->sha1);
+ return ret;
+}
+
int write_locked_index(struct index_state *istate, struct lock_file *lock,
unsigned flags)
{
@@ -2020,6 +2069,12 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
return do_write_locked_index(istate, lock, flags);
}
+ if (istate->cache_changed & SPLIT_INDEX_ORDERED) {
+ int ret = write_shared_index(istate);
+ if (ret)
+ return ret;
+ }
+
return write_split_index(istate, lock, flags);
}
diff --git a/split-index.c b/split-index.c
index ee3246f..21485e2 100644
--- a/split-index.c
+++ b/split-index.c
@@ -74,6 +74,29 @@ static void mark_base_index_entries(struct index_state *base)
base->cache[i]->index = i + 1;
}
+void move_cache_to_base_index(struct index_state *istate)
+{
+ struct split_index *si = istate->split_index;
+ int i;
+
+ /*
+ * do not delete old si->base, its index entries may be shared
+ * with istate->cache[]. Accept a bit of leaking here because
+ * this code is only used by short-lived update-index.
+ */
+ si->base = xcalloc(1, sizeof(*si->base));
+ si->base->version = istate->version;
+ /* zero timestamp disables racy test in ce_write_index() */
+ si->base->timestamp = istate->timestamp;
+ ALLOC_GROW(si->base->cache, istate->cache_nr, si->base->cache_alloc);
+ si->base->cache_nr = istate->cache_nr;
+ memcpy(si->base->cache, istate->cache,
+ sizeof(*istate->cache) * istate->cache_nr);
+ mark_base_index_entries(si->base);
+ for (i = 0; i < si->base->cache_nr; i++)
+ si->base->cache[i]->ce_flags &= ~CE_UPDATE_IN_BASE;
+}
+
static void mark_entry_for_delete(size_t pos, void *data)
{
struct index_state *istate = data;
--
1.9.1.346.ga2b5940
--
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