optimize memory issues (#767)

* optimize memory issues

1. introduce jemalloc support, which can dump current memory usage
2. reduce the GlobalEvent broadcaster memory usage.
3. reduce tcp & udp tunnel memory usage

TODO: if peer conn tunnel hangs, the unbounded channel of peer rpc
may consume lots of memory, which should be improved.

* select a port from 15888+ when port is 0

Cargo.lock

@@ -240,9 +240,9 @@ checksum = "7c02d123df017efcdfbd739ef81735b36c5ba83ec3c59c80a9d7ecc718f92e50"
 
 [[package]]
 name = "async-broadcast"
-version = "0.7.1"
+version = "0.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "20cd0e2e25ea8e5f7e9df04578dc6cf5c83577fd09b1a46aaf5c85e1c33f2a7e"
+checksum = "435a87a52755b8f27fcf321ac4f04b2802e337c8c4872923137471ec39c37532"
 dependencies = [
  "event-listener",
  "event-listener-strategy",
@@ -1925,6 +1925,9 @@ dependencies = [
  "http",
  "http_req",
  "humansize",
+ "jemalloc-ctl",
+ "jemalloc-sys",
+ "jemallocator",
  "kcp-sys",
  "machine-uid",
  "mimalloc-rust",
@@ -3715,6 +3718,37 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "jemalloc-ctl"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cffc705424a344c054e135d12ee591402f4539245e8bbd64e6c9eaa9458b63c"
+dependencies = [
+ "jemalloc-sys",
+ "libc",
+ "paste",
+]
+
+[[package]]
+name = "jemalloc-sys"
+version = "0.5.4+5.3.0-patched"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac6c1946e1cea1788cbfde01c993b52a10e2da07f4bac608228d1bed20bfebf2"
+dependencies = [
+ "cc",
+ "libc",
+]
+
+[[package]]
+name = "jemallocator"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a0de374a9f8e63150e6f5e8a60cc14c668226d7a347d8aee1a45766e3c4dd3bc"
+dependencies = [
+ "jemalloc-sys",
+ "libc",
+]
+
 [[package]]
 name = "jni"
 version = "0.19.0"