Remove the freelist from memarea.c

This is in accordance with our usual policy against freelists,
now that working allocators are everywhere.

It should also make memarea.c's coverage higher.

I also doubt that this code ever helped performance.

changes/remove_memarea_freelist

@@ -0,0 +1,4 @@
+  o Removed code:
+    - We no longer maintain an internal freelist in memarea.c. Allocators
+      should be good enough to make this code unnecessary, and it's doubtful
+      that it ever had any performance benefit.

src/common/memarea.c

@@ -105,56 +105,32 @@ struct memarea_t {
   memarea_chunk_t *first; /**< Top of the chunk stack: never NULL. */
 };
 
-/** How many chunks will we put into the freelist before freeing them? */
-#define MAX_FREELIST_LEN 4
-/** The number of memarea chunks currently in our freelist. */
-static int freelist_len=0;
-/** A linked list of unused memory area chunks.  Used to prevent us from
- * spinning in malloc/free loops. */
-static memarea_chunk_t *freelist = NULL;
-
 /** Helper: allocate a new memarea chunk of around <b>chunk_size</b> bytes. */
 static memarea_chunk_t *
-alloc_chunk(size_t sz, int freelist_ok)
+alloc_chunk(size_t sz)
 {
   tor_assert(sz < SIZE_T_CEILING);
-  if (freelist && freelist_ok) {
-    memarea_chunk_t *res = freelist;
-    freelist = res->next_chunk;
-    res->next_chunk = NULL;
-    --freelist_len;
-    CHECK_SENTINEL(res);
-    return res;
-  } else {
-    size_t chunk_size = freelist_ok ? CHUNK_SIZE : sz;
-    memarea_chunk_t *res;
-    chunk_size += SENTINEL_LEN;
-    res = tor_malloc(chunk_size);
-    res->next_chunk = NULL;
-    res->mem_size = chunk_size - CHUNK_HEADER_SIZE - SENTINEL_LEN;
-    res->next_mem = res->U_MEM;
-    tor_assert(res->next_mem+res->mem_size+SENTINEL_LEN ==
-               ((char*)res)+chunk_size);
-    tor_assert(realign_pointer(res->next_mem) == res->next_mem);
-    SET_SENTINEL(res);
-    return res;
-  }
+
+  size_t chunk_size = sz < CHUNK_SIZE ? CHUNK_SIZE : sz;
+  memarea_chunk_t *res;
+  chunk_size += SENTINEL_LEN;
+  res = tor_malloc(chunk_size);
+  res->next_chunk = NULL;
+  res->mem_size = chunk_size - CHUNK_HEADER_SIZE - SENTINEL_LEN;
+  res->next_mem = res->U_MEM;
+  tor_assert(res->next_mem+res->mem_size+SENTINEL_LEN ==
+             ((char*)res)+chunk_size);
+  tor_assert(realign_pointer(res->next_mem) == res->next_mem);
+  SET_SENTINEL(res);
+  return res;
 }
 
-/** Release <b>chunk</b> from a memarea, either by adding it to the freelist
- * or by freeing it if the freelist is already too big. */
+/** Release <b>chunk</b> from a memarea. */
 static void
 chunk_free_unchecked(memarea_chunk_t *chunk)
 {
   CHECK_SENTINEL(chunk);
-  if (freelist_len < MAX_FREELIST_LEN) {
-    ++freelist_len;
-    chunk->next_chunk = freelist;
-    freelist = chunk;
-    chunk->next_mem = chunk->U_MEM;
-  } else {
-    tor_free(chunk);
-  }
+  tor_free(chunk);
 }
 
 /** Allocate and return new memarea. */
@@ -162,7 +138,7 @@ memarea_t *
 memarea_new(void)
 {
   memarea_t *head = tor_malloc(sizeof(memarea_t));
-  head->first = alloc_chunk(CHUNK_SIZE, 1);
+  head->first = alloc_chunk(CHUNK_SIZE);
   return head;
 }
 
@@ -197,19 +173,6 @@ memarea_clear(memarea_t *area)
   area->first->next_mem = area->first->U_MEM;
 }
 
-/** Remove all unused memarea chunks from the internal freelist. */
-void
-memarea_clear_freelist(void)
-{
-  memarea_chunk_t *chunk, *next;
-  freelist_len = 0;
-  for (chunk = freelist; chunk; chunk = next) {
-    next = chunk->next_chunk;
-    tor_free(chunk);
-  }
-  freelist = NULL;
-}
-
 /** Return true iff <b>p</b> is in a range that has been returned by an
  * allocation from <b>area</b>. */
 int
@@ -241,12 +204,12 @@ memarea_alloc(memarea_t *area, size_t sz)
     if (sz+CHUNK_HEADER_SIZE >= CHUNK_SIZE) {
       /* This allocation is too big.  Stick it in a special chunk, and put
        * that chunk second in the list. */
-      memarea_chunk_t *new_chunk = alloc_chunk(sz+CHUNK_HEADER_SIZE, 0);
+      memarea_chunk_t *new_chunk = alloc_chunk(sz+CHUNK_HEADER_SIZE);
       new_chunk->next_chunk = chunk->next_chunk;
       chunk->next_chunk = new_chunk;
       chunk = new_chunk;
     } else {
-      memarea_chunk_t *new_chunk = alloc_chunk(CHUNK_SIZE, 1);
+      memarea_chunk_t *new_chunk = alloc_chunk(CHUNK_SIZE);
       new_chunk->next_chunk = chunk;
       area->first = chunk = new_chunk;
     }

src/common/memarea.h

@@ -18,7 +18,6 @@ char *memarea_strdup(memarea_t *area, const char *s);
 char *memarea_strndup(memarea_t *area, const char *s, size_t n);
 void memarea_get_stats(memarea_t *area,
                        size_t *allocated_out, size_t *used_out);
-void memarea_clear_freelist(void);
 void memarea_assert_ok(memarea_t *area);
 
 #endif

src/or/main.c

@@ -3100,7 +3100,6 @@ tor_free_all(int postfork)
   connection_free_all();
   connection_edge_free_all();
   scheduler_free_all();
-  memarea_clear_freelist();
   nodelist_free_all();
   microdesc_free_all();
   ext_orport_free_all();

src/test/test_dir.c

@@ -497,7 +497,6 @@ test_dir_routerinfo_parsing(void *arg)
 #undef CHECK_FAIL
 #undef CHECK_OK
  done:
-  memarea_clear_freelist();
   routerinfo_free(ri);
 }
 
@@ -601,7 +600,6 @@ test_dir_extrainfo_parsing(void *arg)
 
  done:
   escaped(NULL);
-  memarea_clear_freelist();
   extrainfo_free(ei);
   routerinfo_free(ri);
   digestmap_free((digestmap_t*)map, routerinfo_free_wrapper_);

src/test/test_options.c

@@ -158,7 +158,6 @@ test_options_validate_impl(const char *configuration,
   }
 
  done:
-  memarea_clear_freelist();
   escaped(NULL);
   policies_free_all();
   config_free_lines(cl);
@@ -1949,7 +1948,6 @@ test_options_validate__use_bridges(void *ignored)
 
  done:
   NS_UNMOCK(geoip_get_country);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2187,7 +2185,6 @@ test_options_validate__publish_server_descriptor(void *ignored)
 
  done:
   teardown_capture_of_logs(previous_log);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2263,7 +2260,6 @@ test_options_validate__testing(void *ignored)
 
  done:
   escaped(NULL); // This will free the leaking memory from the previous escaped
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2311,7 +2307,6 @@ test_options_validate__hidserv(void *ignored)
 
  done:
   teardown_capture_of_logs(previous_log);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2336,7 +2331,6 @@ test_options_validate__predicted_ports(void *ignored)
 
  done:
   teardown_capture_of_logs(previous_log);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2539,7 +2533,6 @@ test_options_validate__bandwidth(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2627,7 +2620,6 @@ test_options_validate__circuits(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -2661,7 +2653,6 @@ test_options_validate__port_forwarding(void *ignored)
 
  done:
   free_options_test_data(tdata);
-  memarea_clear_freelist();
   policies_free_all();
   tor_free(msg);
 }
@@ -2691,7 +2682,6 @@ test_options_validate__tor2web(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -2758,7 +2748,6 @@ test_options_validate__rend(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -2878,7 +2867,6 @@ test_options_validate__accounting(void *ignored)
 
  done:
   teardown_capture_of_logs(previous_log);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -3210,7 +3198,6 @@ test_options_validate__proxy(void *ignored)
  done:
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
-  memarea_clear_freelist();
   policies_free_all();
   // sandbox_free_getaddrinfo_cache();
   tor_free(msg);
@@ -3438,7 +3425,6 @@ test_options_validate__control(void *ignored)
 
  done:
   teardown_capture_of_logs(previous_log);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -3511,7 +3497,6 @@ test_options_validate__families(void *ignored)
 
  done:
   teardown_capture_of_logs(previous_log);
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -3536,7 +3521,6 @@ test_options_validate__addr_policies(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -3623,7 +3607,6 @@ test_options_validate__dir_auth(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -3749,7 +3732,6 @@ test_options_validate__transport(void *ignored)
 
  done:
   escaped(NULL); // This will free the leaking memory from the previous escaped
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -3833,7 +3815,6 @@ test_options_validate__constrained_sockets(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -4053,7 +4034,6 @@ test_options_validate__v3_auth(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -4088,7 +4068,6 @@ test_options_validate__virtual_addr(void *ignored)
 
  done:
   escaped(NULL); // This will free the leaking memory from the previous escaped
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);
@@ -4130,7 +4109,6 @@ test_options_validate__exits(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -4299,7 +4277,6 @@ test_options_validate__testing_options(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   teardown_capture_of_logs(previous_log);
   free_options_test_data(tdata);
@@ -4353,7 +4330,6 @@ test_options_validate__accel(void *ignored)
   tor_free(msg);
 
  done:
-  memarea_clear_freelist();
   policies_free_all();
   free_options_test_data(tdata);
   tor_free(msg);