[perl #19332] [PATCH] mark PMCs w/o next_for_GC

[via RT]

# New Ticket Created by  Leopold Toetsch 
# Please include the string:  [perl #19332]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=19332 >


I'll send this first to the list for review.

This patch changes mark_used(PMC *) so that the PMC field next_for_GC 
isn't used anymore (it could be removed now, making a PMC one ptr size 
smaller).

This would allow finally to use one common mark function:

void pobject_lives(PObj* obj)

which is the same as buffer_lives() now looks like (modulo the 
interpreter used for GC_DEBUG).

A short test (5E6 new P0, .PerlUndef) in a loop shows ~1% speed increase 
due to one less instruction in headers.c:get_free_pmc().

Comments welcome,
leo


-- attachment  1 ------------------------------------------------------
url: http://rt.perl.org/rt2/attach/46018/36002/ea1b6f/mark.patch


--- parrot/dod.c        Thu Dec 12 09:07:25 2002
+++ parrot-leo/dod.c    Sat Dec 21 16:28:57 2002
@@ -23,6 +23,7 @@
 extern void flush_register_windows(void);
 static size_t find_common_mask(size_t val1, size_t val2);
 
+#ifdef MARK_USE_NEXT_FOR_GC
 PMC *
 mark_used(PMC *used_pmc, PMC *current_end_of_list)
 {
@@ -49,6 +50,24 @@
     return used_pmc;
 }
 
+#else
+
+static PMC ** mark_list, ** mark_ptr;
+
+PMC *
+mark_used(PMC *used_pmc, PMC *current_end_of_list)
+{
+    if (PObj_is_live_or_free_TESTALL(used_pmc)) {
+        return current_end_of_list;
+    }
+    PObj_live_SET(used_pmc);
+    *mark_ptr++ = used_pmc;
+    *mark_ptr = NULL;
+    return *mark_ptr;
+}
+
+#endif
+
 #if DISABLE_GC_DEBUG
 void
 buffer_lives(struct Parrot_Interp *interpreter, Buffer *buffer)
@@ -120,6 +139,12 @@
     /* We have to start somewhere, and the global stash is a good place */
     last = current = interpreter->perl_stash->stash_hash;
 
+#ifndef MARK_USE_NEXT_FOR_GC
+    mark_list = realloc(mark_list,
+            (interpreter->arena_base->pmc_pool->total_objects + 1) *
+            sizeof(PMC *));
+    mark_ptr = mark_list;
+#endif
     /* mark it as used and get an updated end of list */
     last = mark_used(current, last);
     /* Parrot_base_classname_hash */
@@ -218,7 +243,11 @@
     /* Okay, we've marked the whole root set, and should have a good-sized
      * list 'o things to look at. Run through it */
     prev = NULL;
+#ifdef MARK_USE_NEXT_FOR_GC
     for (; current != prev; current = current->next_for_GC) {
+#else
+    for (j = 0, current = mark_list[0]; current; current = mark_list[++j]) {
+#endif
         UINTVAL bits = PObj_get_FLAGS(current) & mask;
 
         /* mark properties */
--- parrot/headers.c    Sat Dec 21 11:08:06 2002
+++ parrot-leo/headers.c        Sat Dec 21 16:29:50 2002
@@ -60,8 +60,10 @@
     pool->free_list = *(void **)pmc;
 
     PObj_flags_SETTO(pmc, 0);
+#ifdef MARK_USE_NEXT_FOR_GC
     /* Make sure it doesn't seem to be on the GC list */
     pmc->next_for_GC = NULL;
+#endif
 
     return pmc;
 }