Signed-off-by: Jonathan Tan <jonathantanmy@xxxxxxxxxx>
---
> One main benefit of storing on Bloom filter per commit is to avoid
> recomputing hashes at every commit. Currently, this patch only improves
> locality when checking membership at the cost of taking up more space.
> Drop the dependence on the parent oid and then we can save the time
> spent hashing during history queries.
I've removed the hashing of the parent OID here and tried having
per-parent and per-commit hashes for the first 2 parents of each commit
instead of only 1, thus doubling the filter size. The results are not
much of an improvement though:
bloom filter total queries: 66409 definitely not: 56424 maybe: 9985 false positives: 9099 fp ratio: 0.137015
0:01.17
---
bloom-filter.c | 25 ++++++++++++-------------
bloom-filter.h | 4 ++--
commit-graph.c | 13 ++++++++-----
revision.c | 11 +++++------
4 files changed, 27 insertions(+), 26 deletions(-)
diff --git a/bloom-filter.c b/bloom-filter.c
index 39b453908f..10c73c45ae 100644
--- a/bloom-filter.c
+++ b/bloom-filter.c
@@ -11,7 +11,7 @@ void bloom_filter_init(struct bloom_filter *bf, uint32_t commit_nr, uint32_t bit
bf->nr_entries = 0;
bf->commit_nr = commit_nr;
bf->bit_size = bit_size;
- bf->bits = xcalloc(1, commit_nr * bit_size / CHAR_BIT);
+ bf->bits = xcalloc(1, 2 * commit_nr * bit_size / CHAR_BIT);
}
void bloom_filter_free(struct bloom_filter *bf)
@@ -22,24 +22,24 @@ void bloom_filter_free(struct bloom_filter *bf)
}
-static void bloom_filter_set_bits(struct bloom_filter *bf, uint32_t graph_pos, const uint32_t *offsets,
+static void bloom_filter_set_bits(struct bloom_filter *bf, uint32_t graph_pos, int parent_index, const uint32_t *offsets,
int nr_offsets, int nr_entries)
{
int i;
for (i = 0; i < nr_offsets; i++) {
- uint32_t byte_offset = (offsets[i] % bf->bit_size + graph_pos * bf->bit_size) / CHAR_BIT;
+ uint32_t byte_offset = (offsets[i] % bf->bit_size + (2 * graph_pos + parent_index) * bf->bit_size) / CHAR_BIT;
unsigned char mask = 1 << offsets[i] % CHAR_BIT;
bf->bits[byte_offset] |= mask;
}
bf->nr_entries += nr_entries;
}
-static int bloom_filter_check_bits(struct bloom_filter *bf, uint32_t graph_pos, const uint32_t *offsets,
+static int bloom_filter_check_bits(struct bloom_filter *bf, uint32_t graph_pos, int parent_index, const uint32_t *offsets,
int nr)
{
int i;
for (i = 0; i < nr; i++) {
- uint32_t byte_offset = (offsets[i] % bf->bit_size + graph_pos * bf->bit_size) / CHAR_BIT;
+ uint32_t byte_offset = (offsets[i] % bf->bit_size + (2 * graph_pos + parent_index) * bf->bit_size) / CHAR_BIT;
unsigned char mask = 1 << offsets[i] % CHAR_BIT;
if (!(bf->bits[byte_offset] & mask))
return 0;
@@ -48,19 +48,18 @@ static int bloom_filter_check_bits(struct bloom_filter *bf, uint32_t graph_pos,
}
-void bloom_filter_add_hash(struct bloom_filter *bf, uint32_t graph_pos, const unsigned char *hash)
+void bloom_filter_add_hash(struct bloom_filter *bf, uint32_t graph_pos, int parent_index, const unsigned char *hash)
{
uint32_t offsets[GIT_MAX_RAWSZ / sizeof(uint32_t)];
hashcpy((unsigned char*)offsets, hash);
- bloom_filter_set_bits(bf, graph_pos, offsets,
- the_hash_algo->rawsz / sizeof(*offsets), 1);
+ bloom_filter_set_bits(bf, graph_pos, parent_index, offsets, the_hash_algo->rawsz / sizeof(*offsets), 1);
}
-int bloom_filter_check_hash(struct bloom_filter *bf, uint32_t graph_pos, const unsigned char *hash)
+int bloom_filter_check_hash(struct bloom_filter *bf, uint32_t graph_pos, int parent_index, const unsigned char *hash)
{
uint32_t offsets[GIT_MAX_RAWSZ / sizeof(uint32_t)];
hashcpy((unsigned char*)offsets, hash);
- return bloom_filter_check_bits(bf, graph_pos, offsets,
+ return bloom_filter_check_bits(bf, graph_pos, parent_index, offsets,
the_hash_algo->rawsz / sizeof(*offsets));
}
@@ -87,8 +86,8 @@ int bloom_filter_load(struct bloom_filter *bf)
read_in_full(fd, &bf->bit_size, sizeof(bf->bit_size));
if (bf->bit_size % CHAR_BIT)
BUG("invalid size for bloom filter");
- bf->bits = xmalloc(bf->commit_nr * bf->bit_size / CHAR_BIT);
- read_in_full(fd, bf->bits, bf->commit_nr * bf->bit_size / CHAR_BIT);
+ bf->bits = xmalloc(2 * bf->commit_nr * bf->bit_size / CHAR_BIT);
+ read_in_full(fd, bf->bits, 2 * bf->commit_nr * bf->bit_size / CHAR_BIT);
close(fd);
@@ -102,7 +101,7 @@ void bloom_filter_write(struct bloom_filter *bf)
write_in_full(fd, &bf->nr_entries, sizeof(bf->nr_entries));
write_in_full(fd, &bf->commit_nr, sizeof(bf->commit_nr));
write_in_full(fd, &bf->bit_size, sizeof(bf->bit_size));
- write_in_full(fd, bf->bits, bf->commit_nr * bf->bit_size / CHAR_BIT);
+ write_in_full(fd, bf->bits, 2 * bf->commit_nr * bf->bit_size / CHAR_BIT);
close(fd);
}
diff --git a/bloom-filter.h b/bloom-filter.h
index 607649b8db..20e0527451 100644
--- a/bloom-filter.h
+++ b/bloom-filter.h
@@ -18,13 +18,13 @@ void bloom_filter_free(struct bloom_filter *bf);
* Turns the given (SHA1) hash into 5 unsigned ints, and sets the bits at
* those positions (modulo the bitmap's size) in the Bloom filter.
*/
-void bloom_filter_add_hash(struct bloom_filter *bf, uint32_t graph_pos, const unsigned char *hash);
+void bloom_filter_add_hash(struct bloom_filter *bf, uint32_t graph_pos, int parent_index, const unsigned char *hash);
/*
* Turns the given (SHA1) hash into 5 unsigned ints, and checks the bits at
* those positions (modulo the bitmap's size) in the Bloom filter.
* Returns 1 if all those bits are set, 0 otherwise.
*/
-int bloom_filter_check_hash(struct bloom_filter *bf, uint32_t graph_pos, const unsigned char *hash);
+int bloom_filter_check_hash(struct bloom_filter *bf, uint32_t graph_pos, int parent_index, const unsigned char *hash);
void hashxor(const unsigned char *hash1, const unsigned char *hash2,
unsigned char *out);
diff --git a/commit-graph.c b/commit-graph.c
index d21d555611..ca869c10e1 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -716,6 +716,7 @@ static void add_changes_to_bloom_filter(struct bloom_filter *bf,
struct commit *parent,
struct commit *commit,
int index,
+ int parent_index,
struct diff_options *diffopt)
{
int i;
@@ -738,7 +739,6 @@ static void add_changes_to_bloom_filter(struct bloom_filter *bf,
do {
git_hash_ctx ctx;
unsigned char name_hash[GIT_MAX_RAWSZ];
- unsigned char hash[GIT_MAX_RAWSZ];
p = strchrnul(p + 1, '/');
@@ -754,8 +754,7 @@ static void add_changes_to_bloom_filter(struct bloom_filter *bf,
the_hash_algo->update_fn(&ctx, path, p - path);
the_hash_algo->final_fn(name_hash, &ctx);
- hashxor(name_hash, parent->object.oid.hash, hash);
- bloom_filter_add_hash(bf, index, hash);
+ bloom_filter_add_hash(bf, index, parent_index, name_hash);
} while (*p);
diff_free_filepair(diff_queued_diff.queue[i]);
@@ -784,9 +783,13 @@ static void fill_bloom_filter(struct bloom_filter *bf,
struct commit *commit = commits[i];
struct commit_list *parent = commit->parents;
- if (parent)
- add_changes_to_bloom_filter(bf, parent->item, commit, i,
+ if (parent) {
+ add_changes_to_bloom_filter(bf, parent->item, commit, i, 0,
&revs.diffopt);
+ if (parent->next)
+ add_changes_to_bloom_filter(bf, parent->next->item, commit, i, 1,
+ &revs.diffopt);
+ }
display_progress(progress, i);
}
diff --git a/revision.c b/revision.c
index 5a433a5878..5478d08344 100644
--- a/revision.c
+++ b/revision.c
@@ -488,6 +488,7 @@ static void print_bloom_filter_stats_atexit(void)
static int check_maybe_different_in_bloom_filter(struct rev_info *revs,
struct commit *parent,
+ int parent_index,
struct commit *commit)
{
int i;
@@ -513,10 +514,8 @@ static int check_maybe_different_in_bloom_filter(struct rev_info *revs,
for (i = 0; i < revs->pruning.pathspec.nr; i++) {
struct pathspec_item *pi = &revs->pruning.pathspec.items[i];
- unsigned char hash[GIT_MAX_RAWSZ];
- hashxor(pi->name_hash, parent->object.oid.hash, hash);
- if (bloom_filter_check_hash(&bf, commit->graph_pos, hash)) {
+ if (bloom_filter_check_hash(&bf, commit->graph_pos, parent_index, pi->name_hash)) {
/*
* At least one of the interesting pathspecs differs,
* so we can return early and let the diff machinery
@@ -568,8 +567,8 @@ static int rev_compare_tree(struct rev_info *revs,
return REV_TREE_SAME;
}
- if (!nth_parent) {
- bloom_ret = check_maybe_different_in_bloom_filter(revs, parent, commit);
+ if (nth_parent <= 1) {
+ bloom_ret = check_maybe_different_in_bloom_filter(revs, parent, nth_parent, commit);
if (bloom_ret == 0)
return REV_TREE_SAME;
}
@@ -579,7 +578,7 @@ static int rev_compare_tree(struct rev_info *revs,
if (diff_tree_oid(&t1->object.oid, &t2->object.oid, "",
&revs->pruning) < 0)
return REV_TREE_DIFFERENT;
- if (!nth_parent) {
+ if (nth_parent <= 1) {
if (bloom_ret == 1 && tree_difference == REV_TREE_SAME)
bloom_filter_count_false_positive++;
}
--
2.19.0.271.gfe8321ec05.dirty
