1 files changed, 33 insertions, 3 deletions

diff --git a/src/or/relay.c b/src/or/relay.c
index 201f5c3d34..350353e452 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -2433,6 +2433,12 @@ cell_queues_get_total_allocation(void)
   return total_cells_allocated * packed_cell_mem_cost();
 }
 
+/** How long after we've been low on memory should we try to conserve it? */
+#define MEMORY_PRESSURE_INTERVAL (30*60)
+
+/** The time at which we were last low on memory. */
+static time_t last_time_under_memory_pressure = 0;
+
 /** Check whether we've got too much space used for cells.  If so,
  * call the OOM handler and return 1.  Otherwise, return 0. */
 STATIC int
@@ -2441,13 +2447,37 @@ cell_queues_check_size(void)
   size_t alloc = cell_queues_get_total_allocation();
   alloc += buf_get_total_allocation();
   alloc += tor_zlib_get_total_allocation();
-  if (alloc >= get_options()->MaxMemInQueues) {
-    circuits_handle_oom(alloc);
-    return 1;
+  const size_t rend_cache_total = rend_cache_get_total_allocation();
+  alloc += rend_cache_total;
+  if (alloc >= get_options()->MaxMemInQueues_low_threshold) {
+    last_time_under_memory_pressure = approx_time();
+    if (alloc >= get_options()->MaxMemInQueues) {
+      /* If we're spending over 20% of the memory limit on hidden service
+       * descriptors, free them until we're down to 10%.
+       */
+      if (rend_cache_total > get_options()->MaxMemInQueues / 5) {
+        const size_t bytes_to_remove =
+          rend_cache_total - (size_t)(get_options()->MaxMemInQueues / 10);
+        rend_cache_clean_v2_descs_as_dir(time(NULL), bytes_to_remove);
+        alloc -= rend_cache_total;
+        alloc += rend_cache_get_total_allocation();
+      }
+      circuits_handle_oom(alloc);
+      return 1;
+    }
   }
   return 0;
 }
 
+/** Return true if we've been under memory pressure in the last
+ * MEMORY_PRESSURE_INTERVAL seconds. */
+int
+have_been_under_memory_pressure(void)
+{
+  return last_time_under_memory_pressure + MEMORY_PRESSURE_INTERVAL
+    < approx_time();
+}
+
 /**
  * Update the number of cells available on the circuit's n_chan or p_chan's
  * circuit mux.