Author: Remi Meier <[email protected]>
Branch: c8-new-page-handling
Changeset: r1437:4e523f10a999
Date: 2014-09-29 16:42 +0200
http://bitbucket.org/pypy/stmgc/changeset/4e523f10a999/
Log: we must not execute the STM part of the WB twice and make backup
copies more than once
diff --git a/c8/stm/core.c b/c8/stm/core.c
--- a/c8/stm/core.c
+++ b/c8/stm/core.c
@@ -429,7 +429,22 @@
/* add to read set: */
stm_read(obj);
- /* create backup copy (this may cause several page faults XXX): */
+ /* XXX: add overflow number again? n^2 algorithm ahead... */
+ struct list_s *list = STM_PSEGMENT->modified_old_objects;
+ int i, c = list_count(list);
+ for (i = 0; i < c; i += 3) {
+ if (list->items[i] == (uintptr_t)obj) {
+ /* already executed WB once in this transaction. do GC
+ part again: */
+ obj->stm_flags &= ~GCFLAG_WRITE_BARRIER;
+ LIST_APPEND(STM_PSEGMENT->objects_pointing_to_nursery, obj);
+ return;
+ }
+ }
+
+ /* create backup copy (this may cause several page faults
+ XXX: do backup later and maybe allow for having NO_ACCESS
+ pages around anyway (kind of card marking)): */
struct object_s *bk_obj = malloc(obj_size);
memcpy(bk_obj, realobj, obj_size);
@@ -468,7 +483,6 @@
update the shared page in stm_validate() except if it is the sole
reader of it. But then we don't actually know which revision the
page is at. */
/* XXX this is a temporary solution I suppose */
- int i;
for (i = 0; i < NB_SEGMENTS; i++) {
if (i == my_segnum)
continue;
@@ -708,12 +722,14 @@
undo->backup + SLICE_OFFSET(undo->slice),
SLICE_SIZE(undo->slice));
- size_t obj_size = stmcb_size_rounded_up(undo->backup);
+ size_t obj_size = stmcb_size_rounded_up((struct
object_s*)undo->backup);
+ dprintf(("reset_modified_from_backup_copies(%d): obj=%p off=%lu bk=%p
obj_sz=%lu\n",
+ segment_num, obj, SLICE_OFFSET(undo->slice), undo->backup,
obj_size));
+
if (obj_size - SLICE_OFFSET(undo->slice) <= 4096UL) {
/* only free bk copy once (last slice): */
free(undo->backup);
- dprintf(("reset_modified_from_backup_copies(%d): obj=%p
obj_sz=%lu\n",
- segment_num, obj, obj_size));
+ dprintf(("-> free(%p)\n", undo->backup));
}
}
diff --git a/c8/test/test_basic.py b/c8/test/test_basic.py
--- a/c8/test/test_basic.py
+++ b/c8/test/test_basic.py
@@ -810,3 +810,20 @@
self.switch(1) # validate -> R2
assert stm_get_char(lp_char_5, 384 - 1) == 'o'
+
+ def test_repeated_wb(self):
+ lp_char_5 = stm_allocate_old(384)
+
+ self.start_transaction()
+ stm_set_char(lp_char_5, 'i', 384 - 1, False)
+ stm_set_char(lp_char_5, 'i', HDR, False)
+
+ stm_minor_collect()
+
+ stm_set_char(lp_char_5, 'j', 384 - 1, False)
+ stm_set_char(lp_char_5, 'j', HDR, False)
+
+ self.abort_transaction()
+
+ self.check_char_everywhere(lp_char_5, '\0', offset=HDR)
+ self.check_char_everywhere(lp_char_5, '\0', offset=384-1)
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