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authorSverker Eriksson <[email protected]>2015-12-08 18:45:32 +0100
committerSverker Eriksson <[email protected]>2015-12-09 20:18:17 +0100
commit343f461a2810ce3440b1d7c55cda996038071d87 (patch)
treefd762742b6995ce7eec50a2d9714a844533d3807
parentc97f3332aeddf039ee2207196229b9ff07047c72 (diff)
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erts: Optimize hashing in process dictionary
by limiting table sizes to powers of 2. This will change the default size from 10 to 8.
-rw-r--r--erts/emulator/beam/erl_init.c4
-rw-r--r--erts/emulator/beam/erl_process_dict.c21
-rw-r--r--erts/emulator/beam/erl_process_dict.h1
3 files changed, 22 insertions, 4 deletions
diff --git a/erts/emulator/beam/erl_init.c b/erts/emulator/beam/erl_init.c
index d9c3b0dcf4..0a34d91a01 100644
--- a/erts/emulator/beam/erl_init.c
+++ b/erts/emulator/beam/erl_init.c
@@ -197,7 +197,7 @@ Uint32 verbose; /* See erl_debug.h for information about verbose */
int erts_atom_table_size = ATOM_LIMIT; /* Maximum number of atoms */
-int erts_pd_initial_size = 10;
+int erts_pd_initial_size = 8; /* must be power of 2 */
int erts_modified_timing_level;
@@ -1479,7 +1479,7 @@ erl_start(int argc, char **argv)
VERBOSE(DEBUG_SYSTEM, ("using minimum heap size %d\n", H_MIN_SIZE));
} else if (has_prefix("pds", sub_param)) {
arg = get_arg(sub_param+3, argv[i+1], &i);
- if ((erts_pd_initial_size = atoi(arg)) <= 0) {
+ if (!erts_pd_set_initial_size(atoi(arg))) {
erts_fprintf(stderr, "bad initial process dictionary size %s\n", arg);
erts_usage();
}
diff --git a/erts/emulator/beam/erl_process_dict.c b/erts/emulator/beam/erl_process_dict.c
index e497267b63..c56a722542 100644
--- a/erts/emulator/beam/erl_process_dict.c
+++ b/erts/emulator/beam/erl_process_dict.c
@@ -80,6 +80,8 @@
#define ARRAY_GET(PDict, Index) (((PDict)->size > (Index)) ? \
(PDict)->data[Index] : NIL)
+#define IS_POW2(X) ((X) && !((X) & ((X)-1)))
+
/*
* Forward decalarations
*/
@@ -138,6 +140,16 @@ static void pd_check(ProcDict *pd);
** External interface
*/
+int
+erts_pd_set_initial_size(int size)
+{
+ if (size <= 0)
+ return 0;
+
+ erts_pd_initial_size = 1 << erts_fit_in_bits_uint(size-1);
+ return 1;
+}
+
/*
* Called from break handler
*/
@@ -399,6 +411,7 @@ Eterm erts_pd_hash_get_with_hx(Process *p, Uint32 hx, Eterm id)
unsigned int hval;
ProcDict *pd = p->dictionary;
+ ASSERT(hx == MAKE_HASH(id));
if (pd == NULL)
return am_undefined;
hval = pd_hash_value_to_ix(pd, hx);
@@ -570,6 +583,7 @@ static Eterm pd_hash_put(Process *p, Eterm id, Eterm value)
/* Create it */
array_put(&(p->dictionary), INITIAL_SIZE - 1, NIL);
p->dictionary->homeSize = INITIAL_SIZE;
+ ASSERT(IS_POW2(p->dictionary->homeSize));
}
hval = pd_hash_value(p->dictionary, id);
old = ARRAY_GET(p->dictionary, hval);
@@ -954,9 +968,12 @@ static Eterm array_put(ProcDict **ppdict, unsigned int ndx, Eterm term)
static unsigned int pd_hash_value_to_ix(ProcDict *pdict, Uint32 hx)
{
Uint high;
- high = hx % (pdict->homeSize*2);
+
+ ASSERT(IS_POW2(pdict->homeSize));
+
+ high = hx & (pdict->homeSize*2 - 1);
if (high >= HASH_RANGE(pdict))
- return hx % pdict->homeSize;
+ return hx & (pdict->homeSize - 1);
return high;
}
diff --git a/erts/emulator/beam/erl_process_dict.h b/erts/emulator/beam/erl_process_dict.h
index 9aa21b7c38..ab50d45c63 100644
--- a/erts/emulator/beam/erl_process_dict.h
+++ b/erts/emulator/beam/erl_process_dict.h
@@ -31,6 +31,7 @@ typedef struct proc_dict {
Eterm data[1]; /* The beginning of an array of erlang terms */
} ProcDict;
+int erts_pd_set_initial_size(int size);
Uint erts_dicts_mem_size(struct process *p);
void erts_erase_dicts(struct process *p);
void erts_dictionary_dump(int to, void *to_arg, ProcDict *pd);