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authorLukas Larsson <[email protected]>2017-10-18 15:34:10 +0200
committerLukas Larsson <[email protected]>2017-11-20 09:58:05 +0100
commit10912210641fe7d784c4ba6398c24504200ed339 (patch)
tree4d82ed01baadd9b77d0750fbef369b93056953ab /erts/emulator
parent2994bda075a5119cd3b1d499b5897a3d1befdc6b (diff)
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erts: Limit size of first iterator for hashmaps
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/erl_map.c53
1 files changed, 33 insertions, 20 deletions
diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c
index cbbd62f1a2..8047a9567f 100644
--- a/erts/emulator/beam/erl_map.c
+++ b/erts/emulator/beam/erl_map.c
@@ -2992,20 +2992,6 @@ static Eterm hashmap_bld_tuple_uint(Uint **hpp, Uint *szp, Uint n, Uint nums[])
#define PATH_ELEM(PATH) ((PATH) & PATH_ELEM_MASK)
#define PATH_ELEMS_PER_DIGIT (sizeof(ErtsDigit) * 8 / PATH_ELEM_SIZE)
-/* How many elements we return in one call depends on the number of reductions
- that the process has left to run. In debug we return fewer elements to test
- the Path implementation better. */
-#if defined(DEBUG)
-#define FCALLS_ELEMS(BIF_P) ((BIF_P->fcalls / 4) & 0xF)
-#else
-#define FCALLS_ELEMS(BIF_P) (BIF_P->fcalls / 4)
-#endif
-
-#define NUM_ELEMS_TO_RETURN(BIF_P, map) \
- ((MAX(FCALLS_ELEMS(BIF_P), 1) < hashmap_size(map)) ? \
- MAX(FCALLS_ELEMS(BIF_P), 1) : hashmap_size(map))
-
-
BIF_RETTYPE erts_internal_map_next_3(BIF_ALIST_3) {
Eterm path, map;
@@ -3059,7 +3045,7 @@ BIF_RETTYPE erts_internal_map_next_3(BIF_ALIST_3) {
Uint curr_path;
Uint path_length = 0;
Uint *path_rest = NULL;
- int i, elems = NUM_ELEMS_TO_RETURN(BIF_P, map);
+ int i, elems, orig_elems;
Eterm node = map, res, *path_ptr = NULL, *hp;
/* A stack WSTACK is used when traversing the hashmap.
@@ -3080,12 +3066,37 @@ BIF_RETTYPE erts_internal_map_next_3(BIF_ALIST_3) {
ASSERT(is_hashmap(node));
+/* How many elements we return in one call depends on the number of reductions
+ * that the process has left to run. In debug we return fewer elements to test
+ * the Path implementation better.
+ *
+ * Also, when the path is 0 (i.e. for the first call) we limit the number of
+ * elements to MAP_SMALL_MAP_LIMIT in order to not use a huge amount of heap
+ * when only the first X associations in the hashmap was needed.
+ */
+#if defined(DEBUG)
+#define FCALLS_ELEMS(BIF_P) ((BIF_P->fcalls / 4) & 0xF)
+#else
+#define FCALLS_ELEMS(BIF_P) (BIF_P->fcalls / 4)
+#endif
+
+ if (MAX(FCALLS_ELEMS(BIF_P), 1) < hashmap_size(map))
+ elems = MAX(FCALLS_ELEMS(BIF_P), 1);
+ else
+ elems = hashmap_size(map);
+
+#undef FCALLS_ELEMS
+
if (is_small(path)) {
curr_path = unsigned_val(path);
+
+ if (curr_path == 0 && elems > MAP_SMALL_MAP_LIMIT) {
+ elems = MAP_SMALL_MAP_LIMIT;
+ }
} else if (is_big(path)) {
Eterm *big = big_val(path);
if (bignum_header_is_neg(*big))
- goto badarg;
+ BIF_ERROR(BIF_P, BADARG);
path_length = BIG_ARITY(big) - 1;
curr_path = BIG_DIGIT(big, 0);
path_rest = BIG_V(big) + 1;
@@ -3096,15 +3107,17 @@ BIF_RETTYPE erts_internal_map_next_3(BIF_ALIST_3) {
if (type == iterator) {
/* iterator uses the format {K, V, {K, V, {K, V, [Path | Map]}}},
* so each element is 4 words large */
- hp = HAlloc(BIF_P, 4 * NUM_ELEMS_TO_RETURN(BIF_P, map));
+ hp = HAlloc(BIF_P, 4 * elems);
res = am_none;
} else {
/* list used the format [Path, Map, {K,V}, {K,V} | BIF_ARG_3],
* so each element is 2+3 words large */
- hp = HAlloc(BIF_P, (2 + 3) * NUM_ELEMS_TO_RETURN(BIF_P, map));
+ hp = HAlloc(BIF_P, (2 + 3) * elems);
res = BIF_ARG_3;
}
+ orig_elems = elems;
+
/* First we look for the leaf to start at using the
path given. While doing so, we push each map node
and the index onto the stack to use later. */
@@ -3274,7 +3287,7 @@ BIF_RETTYPE erts_internal_map_next_3(BIF_ALIST_3) {
HRelease(BIF_P, hp + (2+3) * elems, hp);
}
}
- BIF_P->fcalls -= 4 * (NUM_ELEMS_TO_RETURN(BIF_P, map) - elems);
+ BIF_P->fcalls -= 4 * (orig_elems - elems);
DESTROY_WSTACK(stack);
BIF_RET(res);
@@ -3284,7 +3297,7 @@ BIF_RETTYPE erts_internal_map_next_3(BIF_ALIST_3) {
} else {
HRelease(BIF_P, hp + (2+3) * elems, hp);
}
- BIF_P->fcalls -= 4 * (NUM_ELEMS_TO_RETURN(BIF_P, map) - elems);
+ BIF_P->fcalls -= 4 * (orig_elems - elems);
DESTROY_WSTACK(stack);
BIF_ERROR(BIF_P, BADARG);
}