Re: [Help-smalltalk] Big objects and GC

[Paolo Bonzini]

Here is the patch, all the tests are green ;-)

Nice patch!

I have a few comments.

diff --git a/libgst/oop.c b/libgst/oop.c
index ad264d9..018ec95 100644
--- a/libgst/oop.c
+++ b/libgst/oop.c
@@ -66,6 +66,7 @@

 /* Define this flag to turn on debugging code for OOP table management */
 /* #define GC_DEBUGGING */
+#define GC_DEBUGGING

Spurious change.

@@ -701,7 +702,7 @@ _gst_make_oop_fixed (OOP oop)
 {
   gst_object newObj;
   int size;
-  if (oop->flags & F_FIXED)
+  if ((oop->flags & F_FIXED) || (oop->flags & F_LARGE))
     return;

Can you try representing large objects with F_FIXED but not F_OLD?  At 
the same time, makeFixed would not cause objects to become old, which is 
useful for objects passed to C.

Apparently, I even had some code to handle this in _gst_tenure_oop:

  if (oop->flags & F_OLD)
    return;

  if (!(oop->flags & F_FIXED))
    {
      int size = SIZE_TO_BYTES (TO_INT(oop->object->objSize));
      newObj = (gst_object) _gst_mem_alloc (_gst_mem.old, size);
      if (!newObj)
        abort ();

      memcpy (newObj, oop->object, size);
      _gst_mem.numOldOOPs++;

      oop->object = newObj;
    }

where the increment of numOldOOPs should be moved outside the if.

@@ -780,6 +781,38 @@ _gst_alloc_obj (size_t size,
 }

 gst_object
+_gst_alloc_large_obj (size_t size,
+                      OOP *p_oop)
+{
+  gst_object p_instance;
+
+  size = ROUNDED_BYTES (size);
+
+  /* If the object is big enough, we put it directly in fixedspace.  */
+  p_instance = (gst_object) _gst_mem_alloc (_gst_mem.fixed, size);
+  if COMMON (p_instance)
+    goto ok;
+
+  _gst_global_gc (size);
+  p_instance = (gst_object) _gst_mem_alloc (_gst_mem.fixed, size);
+  if COMMON (p_instance)
+    goto ok;
+
+  _gst_compact (0);

Compacting is not going to be helpful, for fixed objects.

@@ -1452,7 +1485,7 @@ _gst_sweep_oop (OOP oop)
     _gst_make_oop_non_weak (oop);

   /* Free unreachable oldspace objects.  */
-  if UNCOMMON (oop->flags & F_FIXED)
+  if UNCOMMON ((oop->flags & F_FIXED) || (oop->flags & F_LARGE))
     {
       _gst_mem.numOldOOPs--;

This makes stats wrong.  With the idea above, the code would be like:

  if ((oop->flags & F_LOADED) == 0)
    {
      if UNCOMMON (oop->flags & F_FIXED)
        _gst_mem_free (_gst_mem.fixed, oop->object);
      else if UNCOMMON (oop->flags & F_OLD)
        _gst_mem_free (_gst_mem.old, oop->object);
    }

  if UNCOMMON (oop->flags & F_OLD)
    {
      _gst_mem.numOldOOPs--;
      stats.reclaimedOldSpaceBytesSinceLastGlobalGC +=
        SIZE_TO_BYTES (TO_INT (OOP_TO_OBJ (oop)->objSize));
    }

It is a very good start though, thanks!

Paolo

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