How the Nasal GC works: Difference between revisions

How the Nasal GC works (view source)

1,073 bytes added , 20 May 2012

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 This also means that we basically just need to provide an alternate naGC_get() function, next to the existing one, to add support for alternate GC schemes.
+= Disabling the current GC =
+The overhead caused by managing the memory pools and constantly scanning the  heap (mark/reap) can be examined by modifying the naGC_get() function such that it no longer uses any pool memory, but directly allocates malloc()/naAlloc() - without ever freeing any memory (i.e. leaking). While the fgfs process will eventually get killed this way, the GC will be basically switched off.
+<syntaxhighlight lang="C">
+struct naObj** naGC_get(struct naPool* p, int n, int* nout)
+{
+    struct naObj** result;
+    naCheckBottleneck();
+    LOCK();
+#define LEAKY
+#ifndef LEAKY
+    while(globals->allocCount < 0 || (p->nfree == 0 && p->freetop >= p->freesz)) {
+        globals->needGC = 1;
+        bottleneck();
+    }
+    if(p->nfree == 0)
+        newBlock(p, poolsize(p)/8);
+    n = p->nfree < n ? p->nfree : n;
+    *nout = n;
+    p->nfree -= n;
+    globals->allocCount -= n;
+    result = (struct naObj**)(p->free + p->nfree);
+#else
+    result = (struct naObj**) naAlloc( naTypeSize(n) );
+#endif
+    UNLOCK();
+    return result;
+}
+</syntaxhighlight>
 = bottleneck() =