From 38d4debb6d180ca53fcb12b8115e81fd4c5262d0 Mon Sep 17 00:00:00 2001 From: Dan McGee Date: Tue, 18 Oct 2011 00:21:23 -0500 Subject: [PATCH] pack-objects: don't traverse objects unnecessarily This brings back some of the performance lost in optimizing recency order inside pack objects. We were doing extreme amounts of object re-traversal: for the 2.14 million objects in the Linux kernel repository, we were calling add_to_write_order() over 1.03 billion times (a 0.2% hit rate, making 99.8% of of these calls extraneous). Two optimizations take place here- we can start our objects array iteration from a known point where we left off before we started trying to find our tags, and we don't need to do the deep dives required by add_family_to_write_order() if the object has already been marked as filled. These two optimizations bring some pretty spectacular results via `perf stat`: task-clock: 83373 ms --> 43800 ms (50% faster) cycles: 221,633,461,676 --> 116,307,209,986 (47% fewer) instructions: 149,299,179,939 --> 122,998,800,184 (18% fewer) Helped-by: Ramsay Jones (format string fix in "die" message) Signed-off-by: Dan McGee Signed-off-by: Junio C Hamano --- builtin/pack-objects.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index 5b544bf44..80ab6c39f 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -520,7 +520,7 @@ static void add_family_to_write_order(struct object_entry **wo, static struct object_entry **compute_write_order(void) { - unsigned int i, wo_end; + unsigned int i, wo_end, last_untagged; struct object_entry **wo = xmalloc(nr_objects * sizeof(*wo)); @@ -551,7 +551,7 @@ static struct object_entry **compute_write_order(void) for_each_tag_ref(mark_tagged, NULL); /* - * Give the commits in the original recency order until + * Give the objects in the original recency order until * we see a tagged tip. */ for (i = wo_end = 0; i < nr_objects; i++) { @@ -559,6 +559,7 @@ static struct object_entry **compute_write_order(void) break; add_to_write_order(wo, &wo_end, &objects[i]); } + last_untagged = i; /* * Then fill all the tagged tips. @@ -571,7 +572,7 @@ static struct object_entry **compute_write_order(void) /* * And then all remaining commits and tags. */ - for (i = 0; i < nr_objects; i++) { + for (i = last_untagged; i < nr_objects; i++) { if (objects[i].type != OBJ_COMMIT && objects[i].type != OBJ_TAG) continue; @@ -581,7 +582,7 @@ static struct object_entry **compute_write_order(void) /* * And then all the trees. */ - for (i = 0; i < nr_objects; i++) { + for (i = last_untagged; i < nr_objects; i++) { if (objects[i].type != OBJ_TREE) continue; add_to_write_order(wo, &wo_end, &objects[i]); @@ -590,8 +591,13 @@ static struct object_entry **compute_write_order(void) /* * Finally all the rest in really tight order */ - for (i = 0; i < nr_objects; i++) - add_family_to_write_order(wo, &wo_end, &objects[i]); + for (i = last_untagged; i < nr_objects; i++) { + if (!objects[i].filled) + add_family_to_write_order(wo, &wo_end, &objects[i]); + } + + if (wo_end != nr_objects) + die("ordered %u objects, expected %"PRIu32, wo_end, nr_objects); return wo; } -- 2.30.2