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avoid traversing table of JITted code names on every GC

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The table as a tree is traversed to prune empty branches,
but the travseral is needed only toward branches that
have changed. Skipping the traversal can save several
milliseconds on each collection.
This commit is contained in:
Matthew Flatt 2015-09-07 19:05:09 -06:00
parent c401d86bb3
commit 7eee429705
1 changed files with 16 additions and 2 deletions
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18
racket/src/racket/src/codetab.inc
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@ -19,6 +19,7 @@ extern MZ_DLLIMPORT int GC_is_marked(void *);
#define NODE_HEADER_SIZE 3
#define NODE_STARTS_OFFSET 1
#define NODE_GCABLE_OFFSET 2
#define NODE_MODIFIED_OFFSET 2
/* Represent a node in the tree as an array of
NODE_HEADER_SIZE + KEY_COUNT pointers.
@ -34,7 +35,10 @@ extern MZ_DLLIMPORT int GC_is_marked(void *);
The third "pointer" is similar to the first, but it represents the
GC status of the reference for CGC, and the bit is only used at a
range start.
range start. For precise GC, this "pointer" is used to indicate
when the array has changed and should be scanned for being
completely empty; it's ok for that flag to be approximate due to
a GC happening while arrays are being modified.
Then there are KEY_COUNT "key" pointers for the content of the
node. Note that KEY_COUNT is smaller than the number of bits
@ -177,6 +181,11 @@ void scheme_jit_add_symbol(uintptr_t start, uintptr_t end, void *value, int gc_a
t1 = t2 = the_tree;
split_t = NULL;
while (offset) {
#ifdef MZ_PRECISE_GC
/* mark as modified */
t1[NODE_MODIFIED_OFFSET] = (void *)0x1;
t2[NODE_MODIFIED_OFFSET] = (void *)0x1;
#endif
offset -= LOG_KEY_SIZE;
k1 = ((start >> offset) & KEY_MASK) + NODE_HEADER_SIZE;
@ -341,10 +350,16 @@ static void check_clear_symbols(void **t)
void *val, **subt;
#ifdef MZ_PRECISE_GC
# if 0
if (((uintptr_t *)t)[NODE_GCABLE_OFFSET] != 0x1)
printf("Found GCed\n");
# endif
#endif
if (!t[NODE_MODIFIED_OFFSET])
return;
t[NODE_MODIFIED_OFFSET] = NULL;
for (i = 0; i < KEY_COUNT; i++) {
val = t[i + NODE_HEADER_SIZE];
@ -359,7 +374,6 @@ static void check_clear_symbols(void **t)
}
if (j == KEY_COUNT) {
t[i+NODE_HEADER_SIZE] = NULL;
// should_have_cleared();
}
}
}