address follow-up comments from 50137

Author: d-netto

src/gc.c

@@ -1238,7 +1238,10 @@ static NOINLINE jl_taggedvalue_t *gc_add_page(jl_gc_pool_t *p) JL_NOTSAFEPOINT
     // Do not pass in `ptls` as argument. This slows down the fast path
     // in pool_alloc significantly
     jl_ptls_t ptls = jl_current_task->ptls;
-    jl_gc_pagemeta_t *pg = jl_gc_alloc_page();
+    jl_gc_pagemeta_t *pg = pop_page_metadata_back(&ptls->page_metadata_lazily_freed);
+    if (pg == NULL) {
+        pg = jl_gc_alloc_page();
+    }
     pg->osize = p->osize;
     pg->thread_n = ptls->tid;
     set_page_metadata(pg);
@@ -1295,20 +1298,8 @@ STATIC_INLINE jl_value_t *jl_gc_pool_alloc_inner(jl_ptls_t ptls, int pool_offset
             assert(pg->osize == p->osize);
             pg->nfree = 0;
             pg->has_young = 1;
-            pg = pop_page_metadata_back(&ptls->page_metadata_lazily_freed);
-            if (pg != NULL) {
-                v = gc_reset_page(ptls, p, pg);
-                pg->osize = p->osize;
-                push_page_metadata_back(&ptls->page_metadata_allocd, pg);
-            }
-            else {
-                v = NULL;
-            }
-        }
-        // Not an else!!
-        if (v == NULL) {
-            v = gc_add_page(p);
         }
+        v = gc_add_page(p);
         next = (jl_taggedvalue_t*)((char*)v + osize);
     }
     p->newpages = next;
@@ -1353,15 +1344,19 @@ static jl_taggedvalue_t **gc_sweep_page(jl_gc_pool_t *p, jl_gc_pagemeta_t **allo
     char *data = pg->data;
     jl_taggedvalue_t *v = (jl_taggedvalue_t*)(data + GC_PAGE_OFFSET);
     char *lim = data + GC_PAGE_SZ - osize;
+    char *lim_newpages = data + GC_PAGE_SZ;
+    if (gc_page_data((char*)p->newpages - 1) == data) {
+        lim_newpages = (char*)p->newpages;
+    }
     size_t old_nfree = pg->nfree;
     size_t nfree;
 
-    int reuse_page = 1;
+    int re_use_page = 1;
     int freed_lazily = 0;
     int freedall = 1;
     int pg_skpd = 1;
     if (!pg->has_marked) {
-        reuse_page = 0;
+        re_use_page = 0;
     #ifdef _P64 // TODO: re-enable on `_P32`?
         // lazy version: (empty) if the whole page was already unused, free it (return it to the pool)
         // eager version: (freedall) free page as soon as possible
@@ -1402,7 +1397,9 @@ static jl_taggedvalue_t **gc_sweep_page(jl_gc_pool_t *p, jl_gc_pagemeta_t **allo
         jl_taggedvalue_t **pfl_begin = NULL;
         while ((char*)v <= lim) {
             int bits = v->bits.gc;
-            if (!gc_marked(bits)) {
+            // if an object is past `lim_newpages` then we can guarantee it's garbage
+            if (!gc_marked(bits) || (char*)v >= lim_newpages) {
+                v->bits.gc = GC_CLEAN;
                 *pfl = v;
                 pfl = &v->next;
                 pfl_begin = (pfl_begin != NULL) ? pfl_begin : pfl;
@@ -1439,7 +1436,7 @@ static jl_taggedvalue_t **gc_sweep_page(jl_gc_pool_t *p, jl_gc_pagemeta_t **allo
     nfree = pg->nfree;
 
 done:
-    if (reuse_page) {
+    if (re_use_page) {
         push_page_metadata_back(allocd, pg);
     }
     else if (freed_lazily) {