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, 62 insertions, 0 deletions

diff --git a/src/debug.c b/src/debug.c
index 0c6b5630c..c82c99b1f 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -297,6 +297,56 @@ void computeDatasetDigest(unsigned char *final) {
     }
 }
 
+#ifdef USE_JEMALLOC
+void mallctl_int(client *c, robj **argv, int argc) {
+    int ret;
+    /* start with the biggest size (int64), and if that fails, try smaller sizes (int32, bool) */
+    int64_t old = 0, val;
+    if (argc > 1) {
+        long long ll;
+        if (getLongLongFromObjectOrReply(c, argv[1], &ll, NULL) != C_OK)
+            return;
+        val = ll;
+    }
+    size_t sz = sizeof(old);
+    while (sz > 0) {
+        if ((ret=je_mallctl(argv[0]->ptr, &old, &sz, argc > 1? &val: NULL, argc > 1?sz: 0))) {
+            if (ret==EINVAL) {
+                /* size might be wrong, try a smaller one */
+                sz /= 2;
+#if BYTE_ORDER == BIG_ENDIAN
+                val <<= 8*sz;
+#endif
+                continue;
+            }
+            addReplyErrorFormat(c,"%s", strerror(ret));
+            return;
+        } else {
+#if BYTE_ORDER == BIG_ENDIAN
+            old >>= 64 - 8*sz;
+#endif
+            addReplyLongLong(c, old);
+            return;
+        }
+    }
+    addReplyErrorFormat(c,"%s", strerror(EINVAL));
+}
+
+void mallctl_string(client *c, robj **argv, int argc) {
+    int ret;
+    char *old;
+    size_t sz = sizeof(old);
+    /* for strings, it seems we need to first get the old value, before overriding it. */
+    if ((ret=je_mallctl(argv[0]->ptr, &old, &sz, NULL, 0))) {
+        addReplyErrorFormat(c,"%s", strerror(ret));
+        return;
+    }
+    addReplyBulkCString(c, old);
+    if(argc > 1)
+        je_mallctl(argv[0]->ptr, NULL, 0, &argv[1]->ptr, sizeof(char*));
+}
+#endif
+
 void debugCommand(client *c) {
     if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"help")) {
         const char *help[] = {
@@ -323,6 +373,10 @@ void debugCommand(client *c) {
 "STRUCTSIZE -- Return the size of different Redis core C structures.",
 "ZIPLIST <key> -- Show low level info about the ziplist encoding.",
 "STRINGMATCH-TEST -- Run a fuzz tester against the stringmatchlen() function.",
+#ifdef USE_JEMALLOC
+"MALLCTL <key> [<val>] -- Get or set a malloc tunning integer.",
+"MALLCTL-STR <key> [<val>] -- Get or set a malloc tunning string.",
+#endif
 NULL
         };
         addReplyHelp(c, help);
@@ -676,6 +730,14 @@ NULL
     {
         stringmatchlen_fuzz_test();
         addReplyStatus(c,"Apparently Redis did not crash: test passed");
+#ifdef USE_JEMALLOC
+    } else if(!strcasecmp(c->argv[1]->ptr,"mallctl") && c->argc >= 3) {
+        mallctl_int(c, c->argv+2, c->argc-2);
+        return;
+    } else if(!strcasecmp(c->argv[1]->ptr,"mallctl-str") && c->argc >= 3) {
+        mallctl_string(c, c->argv+2, c->argc-2);
+        return;
+#endif
     } else {
         addReplySubcommandSyntaxError(c);
         return;