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authorRickard Green <[email protected]>2017-01-23 17:10:18 +0100
committerRickard Green <[email protected]>2017-02-06 19:54:48 +0100
commitb079018e38272604ffacfece9b97924a9e39df5c (patch)
tree87c0c5332a1dd466ba426a6f1ba464ecdc396399 /erts/emulator/beam/external.c
parentaefe39da715130f3d1df10084495d3b7ee48337e (diff)
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Implement magic references
Magic references are *intentionally* indistinguishable from ordinary references for the Erlang software. Magic references do not change the language, and are intended as a pure runtime internal optimization. An ordinary reference is typically used as a key in some table. A magic reference has a direct pointer to a reference counted magic binary. This makes it possible to implement various things without having to do lookups in a table, but instead access the data directly. Besides very fast lookups this can also improve scalability by removing a potentially contended table. A couple of examples of planned future usage of magic references are ETS table identifiers, and BIF timer identifiers. Besides future optimizations using magic references it should also be possible to replace the exposed magic binary cludge with magic references. That is, magic binaries that are exposed as empty binaries to the Erlang software.
Diffstat (limited to 'erts/emulator/beam/external.c')
-rw-r--r--erts/emulator/beam/external.c56
1 files changed, 42 insertions, 14 deletions
diff --git a/erts/emulator/beam/external.c b/erts/emulator/beam/external.c
index 6bcddb9e69..64b17a3f57 100644
--- a/erts/emulator/beam/external.c
+++ b/erts/emulator/beam/external.c
@@ -2579,7 +2579,9 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
ASSERT(dflags & DFLAG_EXTENDED_REFERENCES);
- i = ref_no_of_numbers(obj);
+ erts_magic_ref_save_bin(obj);
+
+ i = ref_no_numbers(obj);
put_int16(i, ep);
ep += 2;
ep = enc_atom(acmp, sysname, ep, dflags);
@@ -3435,26 +3437,35 @@ dec_term_atom_common:
r0 = get_int32(ep); /* allow full word */
ep += 4;
- ref_ext_common:
+ ref_ext_common: {
+ ErtsORefThing *rtp;
+
if (ref_words > ERTS_MAX_REF_NUMBERS)
goto error;
node = dec_get_node(sysname, cre);
if(node == erts_this_node) {
- RefThing *rtp = (RefThing *) hp;
- ref_num = (Uint32 *) (hp + REF_THING_HEAD_SIZE);
+
+ rtp = (ErtsORefThing *) hp;
+ ref_num = &rtp->num[0];
+ if (ref_words != ERTS_REF_NUMBERS) {
+ int i;
+ if (ref_words > ERTS_REF_NUMBERS)
+ goto error; /* Not a ref that we created... */
+ for (i = ref_words; i < ERTS_REF_NUMBERS; i++)
+ ref_num[i] = 0;
+ }
-#if defined(ARCH_64)
- hp += REF_THING_HEAD_SIZE + ref_words/2 + 1;
- rtp->header = make_ref_thing_header(ref_words/2 + 1);
-#else
- hp += REF_THING_HEAD_SIZE + ref_words;
- rtp->header = make_ref_thing_header(ref_words);
+#ifdef ERTS_ORDINARY_REF_MARKER
+ rtp->marker = ERTS_ORDINARY_REF_MARKER;
#endif
+ hp += ERTS_REF_THING_SIZE;
+ rtp->header = ERTS_REF_THING_HEADER;
*objp = make_internal_ref(rtp);
}
else {
ExternalThing *etp = (ExternalThing *) hp;
+ rtp = NULL;
#if defined(ARCH_64)
hp += EXTERNAL_THING_HEAD_SIZE + ref_words/2 + 1;
#else
@@ -3472,12 +3483,13 @@ dec_term_atom_common:
factory->off_heap->first = (struct erl_off_heap_header*)etp;
*objp = make_external_ref(etp);
ref_num = &(etp->data.ui32[0]);
- }
-
#if defined(ARCH_64)
- *(ref_num++) = ref_words /* 32-bit arity */;
+ *(ref_num++) = ref_words /* 32-bit arity */;
#endif
+ }
+
ref_num[0] = r0;
+
for(i = 1; i < ref_words; i++) {
ref_num[i] = get_int32(ep);
ep += 4;
@@ -3486,8 +3498,24 @@ dec_term_atom_common:
if ((1 + ref_words) % 2)
ref_num[ref_words] = 0;
#endif
+ if (node == erts_this_node) {
+ /* Check if it was a magic reference... */
+ ErtsMagicBinary *mb = erts_magic_ref_lookup_bin(ref_num);
+ if (mb) {
+ /*
+ * Was a magic ref; adjust it...
+ *
+ * Refc on binary was increased by lookup above...
+ */
+ ASSERT(rtp);
+ hp = (Eterm *) rtp;
+ write_magic_ref_thing(hp, factory->off_heap, mb);
+ hp += ERTS_MAGIC_REF_THING_SIZE;
+ }
+ }
break;
}
+ }
case BINARY_EXT:
{
n = get_int32(ep);
@@ -4109,7 +4137,7 @@ encode_size_struct_int(TTBSizeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj,
/*fall through*/
case REF_DEF:
ASSERT(dflags & DFLAG_EXTENDED_REFERENCES);
- i = ref_no_of_numbers(obj);
+ i = ref_no_numbers(obj);
result += (1 + 2 + encode_size_struct2(acmp, ref_node_name(obj), dflags) +
1 + 4*i);
break;