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pack-bitmap-write: fill bitmap with commit history 

The current implementation of bitmap_writer_build() creates a
reachability bitmap for every walked commit. After computing a bitmap
for a commit, those bits are pushed to an in-progress bitmap for its
children.

fill_bitmap_commit() assumes the bits corresponding to objects
reachable from the parents of a commit are already set. This means that
when visiting a new commit, we only have to walk the objects reachable
between it and any of its parents.

A future change to bitmap_writer_build() will relax this condition so
not all parents have their bits set. Prepare for that by having
'fill_bitmap_commit()' walk parents until reaching commits whose bits
are already set. Then, walk the trees for these commits as well.

This has no functional change with the current implementation of
bitmap_writer_build().

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2020-12-08 17:04:03 -05:00 committed by Junio C Hamano
parent 010e5eacfb
commit 6dc5ef759f
1 changed files with 23 additions and 7 deletions
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30
pack-bitmap-write.c
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@ -12,6 +12,7 @@
#include "sha1-lookup.h"
#include "pack-objects.h"
#include "commit-reach.h"
#include "prio-queue.h"
struct bitmapped_commit {
struct commit *commit;
@ -279,17 +280,30 @@ static void fill_bitmap_tree(struct bitmap *bitmap,
}
static void fill_bitmap_commit(struct bb_commit *ent,
struct commit *commit)
struct commit *commit,
struct prio_queue *queue)
{
if (!ent->bitmap)
ent->bitmap = bitmap_new();
/*
* mark ourselves, but do not bother with parents; their values
* will already have been propagated to us
*/
bitmap_set(ent->bitmap, find_object_pos(&commit->object.oid));
fill_bitmap_tree(ent->bitmap, get_commit_tree(commit));
prio_queue_put(queue, commit);
while (queue->nr) {
struct commit_list *p;
struct commit *c = prio_queue_get(queue);
bitmap_set(ent->bitmap, find_object_pos(&c->object.oid));
fill_bitmap_tree(ent->bitmap, get_commit_tree(c));
for (p = c->parents; p; p = p->next) {
int pos = find_object_pos(&p->item->object.oid);
if (!bitmap_get(ent->bitmap, pos)) {
bitmap_set(ent->bitmap, pos);
prio_queue_put(queue, p->item);
}
}
}
}
static void store_selected(struct bb_commit *ent, struct commit *commit)
@ -319,6 +333,7 @@ void bitmap_writer_build(struct packing_data *to_pack)
struct bitmap_builder bb;
size_t i;
int nr_stored = 0; /* for progress */
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
writer.bitmaps = kh_init_oid_map();
writer.to_pack = to_pack;
@ -335,7 +350,7 @@ void bitmap_writer_build(struct packing_data *to_pack)
struct commit *child;
int reused = 0;
fill_bitmap_commit(ent, commit);
fill_bitmap_commit(ent, commit, &queue);
if (ent->selected) {
store_selected(ent, commit);
@ -360,6 +375,7 @@ void bitmap_writer_build(struct packing_data *to_pack)
bitmap_free(ent->bitmap);
ent->bitmap = NULL;
}
clear_prio_queue(&queue);
bitmap_builder_clear(&bb);
trace2_region_leave("pack-bitmap-write", "building_bitmaps_total",