commit-graph: Use the commit-graph in revwalks This change makes revwalks a bit faster by using the `commit-graph` file (if present). This is thanks to the `commit-graph` allow much faster parsing of the commit information by requiring near-zero I/O (aside from reading a few dozen bytes off of a `mmap(2)`-ed file) for each commit, instead of having to read the ODB, inflate the commit, and parse it. This is done by modifying `git_commit_list_parse()` and letting it use the ODB-owned commit-graph file. Part of: #5757
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diff --git a/src/commit_list.c b/src/commit_list.c
index 2e103ec..dfdd5da 100644
--- a/src/commit_list.c
+++ b/src/commit_list.c
@@ -124,6 +124,7 @@ static int commit_quick_parse(
return -1;
}
+ node->generation = 0;
node->time = commit->committer->when.time;
node->out_degree = (uint16_t) git_array_size(commit->parent_ids);
node->parents = alloc_parents(walk, node, node->out_degree);
@@ -143,11 +144,38 @@ static int commit_quick_parse(
int git_commit_list_parse(git_revwalk *walk, git_commit_list_node *commit)
{
git_odb_object *obj;
+ git_commit_graph_file *cgraph = NULL;
int error;
if (commit->parsed)
return 0;
+ /* Let's try to use the commit graph first. */
+ git_odb__get_commit_graph(&cgraph, walk->odb);
+ if (cgraph) {
+ git_commit_graph_entry e;
+
+ error = git_commit_graph_entry_find(&e, cgraph, &commit->oid, GIT_OID_RAWSZ);
+ if (error == 0 && git__is_uint16(e.parent_count)) {
+ size_t i;
+ commit->generation = (uint32_t)e.generation;
+ commit->time = e.commit_time;
+ commit->out_degree = (uint16_t)e.parent_count;
+ commit->parents = alloc_parents(walk, commit, commit->out_degree);
+ GIT_ERROR_CHECK_ALLOC(commit->parents);
+
+ for (i = 0; i < commit->out_degree; ++i) {
+ git_commit_graph_entry parent;
+ error = git_commit_graph_entry_parent(&parent, cgraph, &e, i);
+ if (error < 0)
+ return error;
+ commit->parents[i] = git_revwalk__commit_lookup(walk, &parent.sha1);
+ }
+ commit->parsed = 1;
+ return 0;
+ }
+ }
+
if ((error = git_odb_read(&obj, walk->odb, &commit->oid)) < 0)
return error;
diff --git a/src/commit_list.h b/src/commit_list.h
index 6a65f8a..a323770 100644
--- a/src/commit_list.h
+++ b/src/commit_list.h
@@ -26,6 +26,7 @@
typedef struct git_commit_list_node {
git_oid oid;
int64_t time;
+ uint32_t generation;
unsigned int seen:1,
uninteresting:1,
topo_delay:1,
diff --git a/src/odb.c b/src/odb.c
index b2988c4..02f9791 100644
--- a/src/odb.c
+++ b/src/odb.c
@@ -465,6 +465,13 @@ int git_odb_new(git_odb **out)
git__free(db);
return -1;
}
+ if (git_buf_init(&db->objects_dir, 0) < 0) {
+ git_vector_free(&db->backends);
+ git_cache_dispose(&db->own_cache);
+ git_mutex_free(&db->lock);
+ git__free(db);
+ return -1;
+ }
*out = db;
GIT_REFCOUNT_INC(db);
@@ -612,6 +619,17 @@ int git_odb__add_default_backends(
git_mutex_unlock(&db->lock);
#endif
+ if (git_mutex_lock(&db->lock) < 0) {
+ git_error_set(GIT_ERROR_ODB, "failed to acquire the odb lock");
+ return -1;
+ }
+ if (git_buf_len(&db->objects_dir) == 0 && git_buf_sets(&db->objects_dir, objects_dir) < 0) {
+ git_mutex_unlock(&db->lock);
+ git_odb_free(db);
+ return -1;
+ }
+ git_mutex_unlock(&db->lock);
+
/* add the loose object backend */
if (git_odb_backend_loose(&loose, objects_dir, -1, db->do_fsync, 0, 0) < 0 ||
add_backend_internal(db, loose, GIT_LOOSE_PRIORITY, as_alternates, inode) < 0)
@@ -742,6 +760,8 @@ static void odb_free(git_odb *db)
if (locked)
git_mutex_unlock(&db->lock);
+ git_buf_dispose(&db->objects_dir);
+ git_commit_graph_free(db->cgraph);
git_vector_free(&db->backends);
git_cache_dispose(&db->own_cache);
git_mutex_free(&db->lock);
@@ -786,6 +806,53 @@ static int odb_exists_1(
return (int)found;
}
+int git_odb__get_commit_graph(git_commit_graph_file **out, git_odb *db)
+{
+ int error = 0;
+
+ if ((error = git_mutex_lock(&db->lock)) < 0) {
+ git_error_set(GIT_ERROR_ODB, "failed to acquire the db lock");
+ return error;
+ }
+ if (!db->cgraph_checked) {
+ git_buf commit_graph_path = GIT_BUF_INIT;
+ git_commit_graph_file *cgraph = NULL;
+
+ /* We only check once, no matter the result. */
+ db->cgraph_checked = 1;
+
+ if (git_buf_len(&db->objects_dir) == 0) {
+ /*
+ * This odb was not opened with an objects directory
+ * associated. Skip opening the commit graph.
+ */
+ goto done;
+ }
+
+ if ((error = git_buf_joinpath(
+ &commit_graph_path,
+ git_buf_cstr(&db->objects_dir),
+ "info/commit-graph"))
+ < 0) {
+ git_buf_dispose(&commit_graph_path);
+ goto done;
+ }
+ /* Best effort */
+ error = git_commit_graph_open(&cgraph, git_buf_cstr(&commit_graph_path));
+ git_buf_dispose(&commit_graph_path);
+
+ if (error < 0)
+ goto done;
+
+ db->cgraph = cgraph;
+ }
+
+done:
+ *out = db->cgraph;
+ git_mutex_unlock(&db->lock);
+ return 0;
+}
+
static int odb_freshen_1(
git_odb *db,
const git_oid *id,
@@ -1695,6 +1762,13 @@ int git_odb_refresh(struct git_odb *db)
}
}
}
+ if (db->cgraph && git_commit_graph_needs_refresh(db->cgraph, NULL)) {
+ /* We just free the commit graph. The next time it is requested, it will be re-loaded. */
+ git_commit_graph_free(db->cgraph);
+ db->cgraph = NULL;
+ }
+ /* Force a lazy re-check next time it is needed. */
+ db->cgraph_checked = 0;
git_mutex_unlock(&db->lock);
return 0;
diff --git a/src/odb.h b/src/odb.h
index d719856..dcf29c2 100644
--- a/src/odb.h
+++ b/src/odb.h
@@ -13,10 +13,11 @@
#include "git2/oid.h"
#include "git2/types.h"
-#include "vector.h"
#include "cache.h"
-#include "posix.h"
+#include "commit_graph.h"
#include "filter.h"
+#include "posix.h"
+#include "vector.h"
#define GIT_OBJECTS_DIR "objects/"
#define GIT_OBJECT_DIR_MODE 0777
@@ -43,7 +44,10 @@ struct git_odb {
git_mutex lock; /* protects backends */
git_vector backends;
git_cache own_cache;
+ git_buf objects_dir;
+ git_commit_graph_file *cgraph;
unsigned int do_fsync :1;
+ unsigned int cgraph_checked :1;
};
typedef enum {
@@ -127,6 +131,13 @@ int git_odb__read_header_or_object(
git_odb_object **out, size_t *len_p, git_object_t *type_p,
git_odb *db, const git_oid *id);
+/*
+ * Attempt to get the ODB's commit graph. This object is still owned by the
+ * ODB. If the repository does not contain a commit graph, it will return zero
+ * and `*out` will be set to NULL.
+ */
+int git_odb__get_commit_graph(git_commit_graph_file **out, git_odb *odb);
+
/* freshen an entry in the object database */
int git_odb__freshen(git_odb *db, const git_oid *id);