On Wed, Apr 01, 2020 at 06:35:23AM -0400, Jeff King wrote:
> > > + /*
> > > + * this cast works because we only look at the oid part of the entry,
> > > + * and it comes first in the struct
> > > + */
> > > + khiter_t pos = kh_get_object_entry_set(&object_table,
> > > + (struct object_entry *)oid);
> >
> > Dirty, but I can believe the comment.
>
> Our hashmap.c implementation gets around this by letting the equality
> function take an extra parameter. It's annoying when you're writing
> those functions, but it should allow this case without any casting (or
> preemptively allocating a struct).
And here's a patch trying that. Much to my surprise, it outperforms
khash, which has generally been faster in previous tests.
Here are the numbers I get:
nr_objects master khash hashmap
2^20 0m4.317s 0m5.109s 0m3.890s
2^21 0m10.204s 0m9.702s 0m7.933s
2^22 0m27.159s 0m17.911s 0m16.751s
2^23 1m19.038s 0m35.080s 0m31.963s
2^24 4m18.766s 1m10.233s 1m6.793s
And I didn't even have to pre-size the table. This really makes me
wonder if there's some silly inefficiency in khash which we could be
addressing. Or maybe open-addressing really does lose to chaining here,
but I think we keep the load factor low enough that it should be a win.
---
diff --git a/fast-import.c b/fast-import.c
index 202dda11a6..0ef6defc10 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -39,12 +39,28 @@
struct object_entry {
struct pack_idx_entry idx;
- struct object_entry *next;
+ struct hashmap_entry ent;
uint32_t type : TYPE_BITS,
pack_id : PACK_ID_BITS,
depth : DEPTH_BITS;
};
+static int object_entry_hashcmp(const void *map_data,
+ const struct hashmap_entry *eptr,
+ const struct hashmap_entry *entry_or_key,
+ const void *keydata)
+{
+ const struct object_id *oid = keydata;
+ const struct object_entry *e1, *e2;
+
+ e1 = container_of(eptr, const struct object_entry, ent);
+ if (oid)
+ return oidcmp(&e1->idx.oid, oid);
+
+ e2 = container_of(entry_or_key, const struct object_entry, ent);
+ return oidcmp(&e1->idx.oid, &e2->idx.oid);
+}
+
struct object_entry_pool {
struct object_entry_pool *next_pool;
struct object_entry *next_free;
@@ -178,7 +194,7 @@ static off_t pack_size;
/* Table of objects we've written. */
static unsigned int object_entry_alloc = 5000;
static struct object_entry_pool *blocks;
-static struct object_entry *object_table[1 << 16];
+static struct hashmap object_table;
static struct mark_set *marks;
static const char *export_marks_file;
static const char *import_marks_file;
@@ -455,44 +471,42 @@ static struct object_entry *new_object(struct object_id *oid)
static struct object_entry *find_object(struct object_id *oid)
{
- unsigned int h = oid->hash[0] << 8 | oid->hash[1];
- struct object_entry *e;
- for (e = object_table[h]; e; e = e->next)
- if (oideq(oid, &e->idx.oid))
- return e;
+ struct hashmap_entry lookup_entry, *e;
+
+ hashmap_entry_init(&lookup_entry, oidhash(oid));
+ e = hashmap_get(&object_table, &lookup_entry, oid);
+ if (e)
+ return container_of(e, struct object_entry, ent);
return NULL;
}
static struct object_entry *insert_object(struct object_id *oid)
{
- unsigned int h = oid->hash[0] << 8 | oid->hash[1];
- struct object_entry *e = object_table[h];
+ struct object_entry *e;
+ struct hashmap_entry lookup_entry, *hashent;
- while (e) {
- if (oideq(oid, &e->idx.oid))
- return e;
- e = e->next;
- }
+ hashmap_entry_init(&lookup_entry, oidhash(oid));
+ hashent = hashmap_get(&object_table, &lookup_entry, oid);
+ if (hashent)
+ return container_of(hashent, struct object_entry, ent);
e = new_object(oid);
- e->next = object_table[h];
e->idx.offset = 0;
- object_table[h] = e;
+ e->ent.hash = lookup_entry.hash;
+ hashmap_add(&object_table, &e->ent);
return e;
}
static void invalidate_pack_id(unsigned int id)
{
- unsigned int h;
unsigned long lu;
struct tag *t;
+ struct hashmap_iter iter;
+ struct object_entry *e;
- for (h = 0; h < ARRAY_SIZE(object_table); h++) {
- struct object_entry *e;
-
- for (e = object_table[h]; e; e = e->next)
- if (e->pack_id == id)
- e->pack_id = MAX_PACK_ID;
+ hashmap_for_each_entry(&object_table, &iter, e, ent) {
+ if (e->pack_id == id)
+ e->pack_id = MAX_PACK_ID;
}
for (lu = 0; lu < branch_table_sz; lu++) {
@@ -3511,6 +3525,8 @@ int cmd_main(int argc, const char **argv)
avail_tree_table = xcalloc(avail_tree_table_sz, sizeof(struct avail_tree_content*));
marks = mem_pool_calloc(&fi_mem_pool, 1, sizeof(struct mark_set));
+ hashmap_init(&object_table, object_entry_hashcmp, NULL, 0);
+
/*
* We don't parse most options until after we've seen the set of
* "feature" lines at the start of the stream (which allows the command
