make redis purge jemalloc after flush, and enable background purging thread

jemalloc 5 doesn't immediately release memory back to the OS, instead there's a decaying
mechanism, which doesn't work when there's no traffic (no allocations).
this is most evident if there's no traffic after flushdb, the RSS will remain high.

1) enable jemalloc background purging
2) explicitly purge in flushdb

1 files changed, 9 insertions, 0 deletions

diff --git a/src/config.c b/src/config.c
index 7f0e9af89..16850a1fc 100644
--- a/src/config.c
+++ b/src/config.c
@@ -474,6 +474,10 @@ void loadServerConfigFromString(char *config) {
                 err = "active defrag can't be enabled without proper jemalloc support"; goto loaderr;
 #endif
             }
+        } else if (!strcasecmp(argv[0],"jemalloc-bg-thread") && argc == 2) {
+            if ((server.jemalloc_bg_thread = yesnotoi(argv[1])) == -1) {
+                err = "argument must be 'yes' or 'no'"; goto loaderr;
+            }
         } else if (!strcasecmp(argv[0],"daemonize") && argc == 2) {
             if ((server.daemonize = yesnotoi(argv[1])) == -1) {
                 err = "argument must be 'yes' or 'no'"; goto loaderr;
@@ -1153,6 +1157,9 @@ void configSetCommand(client *c) {
         }
 #endif
     } config_set_bool_field(
+      "jemalloc-bg-thread",server.jemalloc_bg_thread) {
+          set_jemalloc_bg_thread(server.jemalloc_bg_thread);
+    } config_set_bool_field(
       "protected-mode",server.protected_mode) {
     } config_set_bool_field(
       "gopher-enabled",server.gopher_enabled) {
@@ -1487,6 +1494,7 @@ void configGetCommand(client *c) {
     config_get_bool_field("rdbchecksum", server.rdb_checksum);
     config_get_bool_field("activerehashing", server.activerehashing);
     config_get_bool_field("activedefrag", server.active_defrag_enabled);
+    config_get_bool_field("jemalloc-bg-thread", server.jemalloc_bg_thread);
     config_get_bool_field("protected-mode", server.protected_mode);
     config_get_bool_field("gopher-enabled", server.gopher_enabled);
     config_get_bool_field("io-threads-do-reads", server.io_threads_do_reads);
@@ -2318,6 +2326,7 @@ int rewriteConfig(char *path) {
     rewriteConfigNumericalOption(state,"hll-sparse-max-bytes",server.hll_sparse_max_bytes,CONFIG_DEFAULT_HLL_SPARSE_MAX_BYTES);
     rewriteConfigYesNoOption(state,"activerehashing",server.activerehashing,CONFIG_DEFAULT_ACTIVE_REHASHING);
     rewriteConfigYesNoOption(state,"activedefrag",server.active_defrag_enabled,CONFIG_DEFAULT_ACTIVE_DEFRAG);
+    rewriteConfigYesNoOption(state,"jemalloc-bg-thread",server.jemalloc_bg_thread,1);
     rewriteConfigYesNoOption(state,"protected-mode",server.protected_mode,CONFIG_DEFAULT_PROTECTED_MODE);
     rewriteConfigYesNoOption(state,"gopher-enabled",server.gopher_enabled,CONFIG_DEFAULT_GOPHER_ENABLED);
     rewriteConfigYesNoOption(state,"io-threads-do-reads",server.io_threads_do_reads,CONFIG_DEFAULT_IO_THREADS_DO_READS);