[pypy-commit] stmgc c7-refactor: Tweaks

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: c7-refactor
Changeset: r812:027470d9d12b
Date: 2014-02-23 14:25 +0100
http://bitbucket.org/pypy/stmgc/changeset/027470d9d12b/

Log:	Tweaks

diff --git a/c7/stm/core.c b/c7/stm/core.c
--- a/c7/stm/core.c
+++ b/c7/stm/core.c
@@ -128,8 +128,14 @@
 
     uint8_t old_rv = STM_SEGMENT->transaction_read_version;
     STM_SEGMENT->transaction_read_version = old_rv + 1;
-    if (UNLIKELY(old_rv == 0xff))
+    if (UNLIKELY(old_rv >= 0xfe)) {
+        /* reset if transaction_read_version was 0xfe or 0xff.  If it's
+           0xff, then we need it because the new value would overflow to
+           0.  But resetting it already from 0xfe is better for short
+           or medium transactions: at the next minor collection we'll
+           still have one free number to increase to. */
         reset_transaction_read_version();
+    }
 
     STM_PSEGMENT->min_read_version_outside_nursery =
         STM_SEGMENT->transaction_read_version;
diff --git a/c7/stm/nursery.c b/c7/stm/nursery.c
--- a/c7/stm/nursery.c
+++ b/c7/stm/nursery.c
@@ -245,18 +245,19 @@
 
 static void trace_and_drag_out_of_nursery(object_t *obj)
 {
-    if (is_in_shared_pages(obj)) {
-        /* the object needs fixing only in one copy, because all copies
-           are shared and identical. */
-        char *realobj = (char *)REAL_ADDRESS(stm_object_pages, obj);
+    long i;
+    for (i = 0; i < NB_SEGMENTS; i++) {
+        struct object_s *realobj =
+            (struct object_s *)REAL_ADDRESS(get_segment_base(i), obj);
+
+        realobj->stm_flags &= ~GCFLAG_WRITE_BARRIER_CALLED;
+
         stmcb_trace((struct object_s *)realobj, &minor_trace_if_young);
-    }
-    else {
-        /* every segment needs fixing */
-        long i;
-        for (i = 0; i < NB_SEGMENTS; i++) {
-            char *realobj = (char *)REAL_ADDRESS(get_segment_base(i), obj);
-            stmcb_trace((struct object_s *)realobj, &minor_trace_if_young);
+
+        if (i == 0 && is_in_shared_pages(obj)) {
+            /* the object needs fixing only in one copy, because all copies
+               are shared and identical. */
+            break;
         }
     }
 }
@@ -274,9 +275,9 @@
         if ((obj->stm_flags & GCFLAG_WRITE_BARRIER_CALLED) == 0)
             continue;
 
-        /* Remove the flag GCFLAG_WRITE_BARRIER_CALLED.  No live object
-           should have this flag set after a nursery collection. */
-        obj->stm_flags &= ~GCFLAG_WRITE_BARRIER_CALLED;
+        /* The flag GCFLAG_WRITE_BARRIER_CALLED is going to be removed:
+           no live object should have this flag set after a nursery
+           collection.  It is done in either one or NB_SEGMENTS copies. */
 
         /* Trace the 'obj' to replace pointers to nursery with pointers
            outside the nursery, possibly forcing nursery objects out