serf: reclaim from persistent memoization cache (#549)

This PR builds on #546, extending it's more-granular state management to
the persistent memoization cache introduced in #508

pkg/vere/serf.c

@@ -193,7 +193,20 @@ u3_serf_grab(void)
 void
 u3_serf_post(u3_serf* sef_u)
 {
-  if ( sef_u->fag_w & (_serf_fag_hit1|_serf_fag_much|_serf_fag_vega) ) {
+  if ( sef_u->fag_w & _serf_fag_hit1 ) {
+    if ( u3C.wag_w & u3o_verbose ) {
+      u3l_log("serf: threshold 1: %u", u3h_wyt(u3R->cax.per_p));
+    }
+    u3h_trim_to(u3R->cax.per_p, u3h_wyt(u3R->cax.per_p) / 2);
+    u3m_reclaim();
+  }
+
+  if ( sef_u->fag_w & _serf_fag_much ) {
+    u3m_reclaim();
+  }
+
+  if ( sef_u->fag_w & _serf_fag_vega ) {
+    u3h_trim_to(u3R->cax.per_p, u3h_wyt(u3R->cax.per_p) / 2);
     u3m_reclaim();
   }
 
@@ -205,6 +218,11 @@ u3_serf_post(u3_serf* sef_u)
   }
 
   if ( sef_u->fag_w & _serf_fag_hit0 ) {
+    if ( u3C.wag_w & u3o_verbose ) {
+      u3l_log("serf: threshold 0: per_p %u", u3h_wyt(u3R->cax.per_p));
+    }
+    u3h_free(u3R->cax.per_p);
+    u3R->cax.per_p = u3h_new_cache(u3C.per_w);
     u3a_print_memory(stderr, "serf: pack: gained", u3m_pack());
     u3l_log("");
   }