[PATCH 5/8] read-cache: try index data from shared memory
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
Documentation/config.txt | 4 ++++
cache.h | 1 +
config.c | 12 ++++++++++++
environment.c | 1 +
read-cache.c | 43 +++++++++++++++++++++++++++++++++++++++++++
submodule.c | 1 +
6 files changed, 62 insertions(+)
diff --git a/Documentation/config.txt b/Documentation/config.txt
index d8b6cc9..ccbe00b 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -617,6 +617,10 @@ 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.
+core.useReadCacheDaemon::
+ Use `git read-cache--daemon` to speed up index reading. See
+ linkgit:git-read-cache--daemon for more information.
+
core.createObject::
You can set this to 'link', in which case a hardlink followed by
a delete of the source are used to make sure that object creation
diff --git a/cache.h b/cache.h
index d0ff11c..fb29c7e 100644
--- a/cache.h
+++ b/cache.h
@@ -603,6 +603,7 @@ extern size_t packed_git_limit;
extern size_t delta_base_cache_limit;
extern unsigned long big_file_threshold;
extern unsigned long pack_size_limit_cfg;
+extern int use_read_cache_daemon;
/*
* Do replace refs need to be checked this run? This variable is
diff --git a/config.c b/config.c
index a30cb5c..5c832ad 100644
--- a/config.c
+++ b/config.c
@@ -874,6 +874,18 @@ static int git_default_core_config(const char *var, const char *value)
return 0;
}
+#ifdef HAVE_SHM
+ /*
+ * Currently git-read-cache--daemon is only built when
+ * HAVE_SHM is set. Ignore user settings if HAVE_SHM is not
+ * defined.
+ */
+ if (!strcmp(var, "core.usereadcachedaemon")) {
+ use_read_cache_daemon = git_config_bool(var, value);
+ return 0;
+ }
+#endif
+
/* Add other config variables here and to Documentation/config.txt. */
return 0;
}
diff --git a/environment.c b/environment.c
index 5c4815d..b76a414 100644
--- a/environment.c
+++ b/environment.c
@@ -63,6 +63,7 @@ int merge_log_config = -1;
int precomposed_unicode = -1; /* see probe_utf8_pathname_composition() */
struct startup_info *startup_info;
unsigned long pack_size_limit_cfg;
+int use_read_cache_daemon;
/*
* The character that begins a commented line in user-editable file
diff --git a/read-cache.c b/read-cache.c
index a5031f3..0e46523 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1462,6 +1462,48 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
return ce;
}
+static void *try_shm(void *mmap, size_t *mmap_size)
+{
+ struct strbuf sb = STRBUF_INIT;
+ size_t old_size = *mmap_size;
+ void *new_mmap;
+ struct stat st;
+ int fd;
+
+ if (old_size <= 20 || !use_read_cache_daemon)
+ return mmap;
+
+ strbuf_addf(&sb, "/git-index-%s.lock",
+ sha1_to_hex((unsigned char *)mmap + old_size - 20));
+ fd = shm_open(sb.buf, O_RDONLY, 0777);
+ if (fd >= 0) {
+ close(fd);
+ return mmap;
+ }
+ strbuf_setlen(&sb, sb.len - 5); /* no ".lock" */
+ fd = shm_open(sb.buf, O_RDONLY, 0777);
+ strbuf_release(&sb);
+ if (fd < 0)
+ /*
+ * git-read-cache--daemon is probably not started yet. For
+ * simplicity, only start it at the next index update, which
+ * should happen often.
+ */
+ return mmap;
+ if (fstat(fd, &st)) {
+ close(fd);
+ return mmap;
+ }
+ new_mmap = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+ close(fd);
+ if (new_mmap == MAP_FAILED)
+ return mmap;
+ munmap(mmap, old_size);
+ *mmap_size = st.st_size;
+ return new_mmap;
+}
+
+
/* remember to discard_cache() before reading a different cache! */
int do_read_index(struct index_state *istate, const char *path, int must_exist)
{
@@ -1501,6 +1543,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
}
close(fd);
+ mmap = try_shm(mmap, &mmap_size);
hdr = mmap;
if (verify_hdr(hdr, mmap_size) < 0)
goto unmap;
diff --git a/submodule.c b/submodule.c
index b80ecac..9872928 100644
--- a/submodule.c
+++ b/submodule.c
@@ -195,6 +195,7 @@ void gitmodules_config(void)
int pos;
strbuf_addstr(&gitmodules_path, work_tree);
strbuf_addstr(&gitmodules_path, "/.gitmodules");
+ git_config(git_default_config, NULL);
if (read_cache() < 0)
die("index file corrupt");
pos = cache_name_pos(".gitmodules", 11);
--
1.9.1.346.ga2b5940
Nguyễn Thái Ngọc Duy <pclouds@gmail.com>