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Bug 479553 - Property tree forking heuristic improvement, r=brendan.

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This commit is contained in:
Graydon Hoare 2009-03-31 17:55:43 -07:00
parent db4fc5fa68
commit 4ef0a7a1ec
1 changed files with 18 additions and 3 deletions
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21
js/src/jsscope.cpp
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@ -1129,15 +1129,30 @@ js_AddScopeProperty(JSContext *cx, JSScope *scope, jsid id,
JS_ASSERT(scope->table);
CHECK_ANCESTOR_LINE(scope, JS_TRUE);
JSBool conflicts = JS_FALSE;
/*
* Our forking heuristic tries to balance the desire to avoid
* over-compacting (over-forking) against the desire to
* *periodically* fork anyways, in order to prevent paying scan
* penalties on each insert indefinitely, on a lineage with only
* a few old middle-deletions. So we fork if either:
*
* - A quick scan finds a true conflict.
* - We are passing through a doubling-threshold in size and
* have accumulated a nonzero count of uncompacted deletions.
*/
bool conflicts = false;
uint32 count = 0;
uint32 threshold = JS_BIT(JS_CeilingLog2(scope->entryCount));
for (sprop = SCOPE_LAST_PROP(scope); sprop; sprop = sprop->parent) {
++count;
if (sprop->id == id) {
conflicts = JS_TRUE;
conflicts = true;
break;
}
}
if (conflicts) {
if (conflicts || count > threshold) {
/*
* Enumerate live entries in scope->table using a temporary
* vector, by walking the (possibly sparse, due to deletions)