diff --git a/src/redis.c b/src/redis.c
index 308168251..bcdba13d8 100644
--- a/src/redis.c
+++ b/src/redis.c
@@ -1062,6 +1062,9 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
     if (zmalloc_used_memory() > server.stat_peak_memory)
         server.stat_peak_memory = zmalloc_used_memory();
 
+    /* Sample the RSS here since this is a relatively slow call. */
+    server.resident_set_size = zmalloc_get_rss();
+
     /* We received a SIGTERM, shutting down here in a safe way, as it is
      * not ok doing so inside the signal handler. */
     if (server.shutdown_asap) {
@@ -1690,6 +1693,7 @@ void initServer() {
     /* A few stats we don't want to reset: server startup time, and peak mem. */
     server.stat_starttime = time(NULL);
     server.stat_peak_memory = 0;
+    server.resident_set_size = 0;
     server.lastbgsave_status = REDIS_OK;
     server.aof_last_write_status = REDIS_OK;
     server.aof_last_write_errno = 0;
@@ -2459,11 +2463,11 @@ sds genRedisInfoString(char *section) {
             "mem_allocator:%s\r\n",
             zmalloc_used,
             hmem,
-            zmalloc_get_rss(),
+            server.resident_set_size,
             server.stat_peak_memory,
             peak_hmem,
             ((long long)lua_gc(server.lua,LUA_GCCOUNT,0))*1024LL,
-            zmalloc_get_fragmentation_ratio(),
+            zmalloc_get_fragmentation_ratio(server.resident_set_size),
             ZMALLOC_LIB
             );
     }
diff --git a/src/redis.h b/src/redis.h
index 5ac794948..fd5dac19c 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -676,6 +676,7 @@ struct redisServer {
     long long slowlog_entry_id;     /* SLOWLOG current entry ID */
     long long slowlog_log_slower_than; /* SLOWLOG time limit (to get logged) */
     unsigned long slowlog_max_len;     /* SLOWLOG max number of items logged */
+    size_t resident_set_size;       /* RSS sampled in serverCron(). */
     /* The following two are used to track instantaneous "load" in terms
      * of operations per second. */
     long long ops_sec_last_sample_time; /* Timestamp of last sample (in ms) */
diff --git a/src/zmalloc.c b/src/zmalloc.c
index e7e97aa67..d0cf726cb 100644
--- a/src/zmalloc.c
+++ b/src/zmalloc.c
@@ -321,8 +321,8 @@ size_t zmalloc_get_rss(void) {
 #endif
 
 /* Fragmentation = RSS / allocated-bytes */
-float zmalloc_get_fragmentation_ratio(void) {
-    return (float)zmalloc_get_rss()/zmalloc_used_memory();
+float zmalloc_get_fragmentation_ratio(size_t rss) {
+    return (float)rss/zmalloc_used_memory();
 }
 
 #if defined(HAVE_PROC_SMAPS)
diff --git a/src/zmalloc.h b/src/zmalloc.h
index 331d8e433..72a4f8138 100644
--- a/src/zmalloc.h
+++ b/src/zmalloc.h
@@ -73,7 +73,7 @@ char *zstrdup(const char *s);
 size_t zmalloc_used_memory(void);
 void zmalloc_enable_thread_safeness(void);
 void zmalloc_set_oom_handler(void (*oom_handler)(size_t));
-float zmalloc_get_fragmentation_ratio(void);
+float zmalloc_get_fragmentation_ratio(size_t rss);
 size_t zmalloc_get_rss(void);
 size_t zmalloc_get_private_dirty(void);
 void zlibc_free(void *ptr);