From 891435d55da80ca3654b19834481205be6bdfe33 Mon Sep 17 00:00:00 2001 From: Derrick Stolee Date: Fri, 6 Apr 2018 19:09:32 +0000 Subject: treewide: rename tree to maybe_tree Using the commit-graph file to walk commit history removes the large cost of parsing commits during the walk. This exposes a performance issue: lookup_tree() takes a large portion of the computation time, even when Git never uses those trees. In anticipation of lazy-loading these trees, rename the 'tree' member of struct commit to 'maybe_tree'. This serves two purposes: it hints at the future role of possibly being NULL even if the commit has a valid tree, and it allows for unambiguous transformation from simple member access (i.e. commit->maybe_tree) to method access. Signed-off-by: Derrick Stolee Signed-off-by: Junio C Hamano --- commit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'commit.c') diff --git a/commit.c b/commit.c index 3e39c86abf..fbc092808c 100644 --- a/commit.c +++ b/commit.c @@ -335,7 +335,7 @@ int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long s if (get_sha1_hex(bufptr + 5, parent.hash) < 0) return error("bad tree pointer in commit %s", oid_to_hex(&item->object.oid)); - item->tree = lookup_tree(&parent); + item->maybe_tree = lookup_tree(&parent); bufptr += tree_entry_len + 1; /* "tree " + "hex sha1" + "\n" */ pptr = &item->parents; -- cgit v1.2.3 From 5bb03de102b40d9e564be3a3a39084a550db79cb Mon Sep 17 00:00:00 2001 From: Derrick Stolee Date: Fri, 6 Apr 2018 19:09:34 +0000 Subject: commit: create get_commit_tree() method While walking the commit graph, we load struct commit objects into the object cache. During this process, we also load struct tree objects for the root tree of each of these commits. We load these objects even if we are only computing commit reachability information, such as a merge base or ahead/behind information. Create get_commit_tree() as a first step to removing direct references to the 'maybe_tree' member of struct commit. Create get_commit_tree_oid() as a shortcut for several references to "&commit->maybe_tree->object.oid" in the codebase. Signed-off-by: Derrick Stolee Signed-off-by: Junio C Hamano --- commit.c | 10 ++++++++++ commit.h | 3 +++ 2 files changed, 13 insertions(+) (limited to 'commit.c') diff --git a/commit.c b/commit.c index fbc092808c..aea2ca1f8b 100644 --- a/commit.c +++ b/commit.c @@ -296,6 +296,16 @@ void free_commit_buffer(struct commit *commit) } } +struct tree *get_commit_tree(const struct commit *commit) +{ + return commit->maybe_tree; +} + +struct object_id *get_commit_tree_oid(const struct commit *commit) +{ + return &get_commit_tree(commit)->object.oid; +} + const void *detach_commit_buffer(struct commit *commit, unsigned long *sizep) { struct commit_buffer *v = buffer_slab_peek(&buffer_slab, commit); diff --git a/commit.h b/commit.h index c4d6e6e064..dc4bf97d9f 100644 --- a/commit.h +++ b/commit.h @@ -102,6 +102,9 @@ void unuse_commit_buffer(const struct commit *, const void *buffer); */ void free_commit_buffer(struct commit *); +struct tree *get_commit_tree(const struct commit *); +struct object_id *get_commit_tree_oid(const struct commit *); + /* * Disassociate any cached object buffer from the commit, but do not free it. * The buffer (or NULL, if none) is returned. -- cgit v1.2.3 From 7b8a21dba1bce44d64bd86427d3d92437adc4707 Mon Sep 17 00:00:00 2001 From: Derrick Stolee Date: Fri, 6 Apr 2018 19:09:46 +0000 Subject: commit-graph: lazy-load trees for commits The commit-graph file provides quick access to commit data, including the OID of the root tree for each commit in the graph. When performing a deep commit-graph walk, we may not need to load most of the trees for these commits. Delay loading the tree object for a commit loaded from the graph until requested via get_commit_tree(). Do not lazy-load trees for commits not in the graph, since that requires duplicate parsing and the relative peformance improvement when trees are not needed is small. On the Linux repository, performance tests were run for the following command: git log --graph --oneline -1000 Before: 0.92s After: 0.66s Rel %: -28.3% Adding '-- kernel/' to the command requires loading the root tree for every commit that is walked. There was no measureable performance change as a result of this patch. Signed-off-by: Derrick Stolee Signed-off-by: Junio C Hamano --- commit-graph.c | 26 +++++++++++++++++++++++--- commit-graph.h | 2 ++ commit.c | 8 +++++++- commit.h | 6 ++++++ 4 files changed, 38 insertions(+), 4 deletions(-) (limited to 'commit.c') diff --git a/commit-graph.c b/commit-graph.c index 264aa6d919..70fa1b25fd 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -247,7 +247,6 @@ static struct commit_list **insert_parent_or_die(struct commit_graph *g, static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos) { - struct object_id oid; uint32_t edge_value; uint32_t *parent_data_ptr; uint64_t date_low, date_high; @@ -257,8 +256,7 @@ static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uin item->object.parsed = 1; item->graph_pos = pos; - hashcpy(oid.hash, commit_data); - item->maybe_tree = lookup_tree(&oid); + item->maybe_tree = NULL; date_high = get_be32(commit_data + g->hash_len + 8) & 0x3; date_low = get_be32(commit_data + g->hash_len + 12); @@ -317,6 +315,28 @@ int parse_commit_in_graph(struct commit *item) return 0; } +static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c) +{ + struct object_id oid; + const unsigned char *commit_data = g->chunk_commit_data + + GRAPH_DATA_WIDTH * (c->graph_pos); + + hashcpy(oid.hash, commit_data); + c->maybe_tree = lookup_tree(&oid); + + return c->maybe_tree; +} + +struct tree *get_commit_tree_in_graph(const struct commit *c) +{ + if (c->maybe_tree) + return c->maybe_tree; + if (c->graph_pos == COMMIT_NOT_FROM_GRAPH) + BUG("get_commit_tree_in_graph called from non-commit-graph commit"); + + return load_tree_for_commit(commit_graph, (struct commit *)c); +} + static void write_graph_chunk_fanout(struct hashfile *f, struct commit **commits, int nr_commits) diff --git a/commit-graph.h b/commit-graph.h index e1d8580c98..260a468e73 100644 --- a/commit-graph.h +++ b/commit-graph.h @@ -17,6 +17,8 @@ char *get_commit_graph_filename(const char *obj_dir); */ int parse_commit_in_graph(struct commit *item); +struct tree *get_commit_tree_in_graph(const struct commit *c); + struct commit_graph { int graph_fd; diff --git a/commit.c b/commit.c index aea2ca1f8b..711f674c18 100644 --- a/commit.c +++ b/commit.c @@ -298,7 +298,13 @@ void free_commit_buffer(struct commit *commit) struct tree *get_commit_tree(const struct commit *commit) { - return commit->maybe_tree; + if (commit->maybe_tree || !commit->object.parsed) + return commit->maybe_tree; + + if (commit->graph_pos == COMMIT_NOT_FROM_GRAPH) + BUG("commit has NULL tree, but was not loaded from commit-graph"); + + return get_commit_tree_in_graph(commit); } struct object_id *get_commit_tree_oid(const struct commit *commit) diff --git a/commit.h b/commit.h index dc4bf97d9f..23a3f364ed 100644 --- a/commit.h +++ b/commit.h @@ -22,6 +22,12 @@ struct commit { unsigned int index; timestamp_t date; struct commit_list *parents; + + /* + * If the commit is loaded from the commit-graph file, then this + * member may be NULL. Only access it through get_commit_tree() + * or get_commit_tree_oid(). + */ struct tree *maybe_tree; uint32_t graph_pos; }; -- cgit v1.2.3