Use Jemalloc (#189)

Jemalloc performs better than the standard allocator in various metrics (http://ithare.com/testing-memory-allocators-ptmalloc2-tcmalloc-hoard-jemalloc-while-trying-to-simulate-real-world-loads/).

This PR makes changes to use Jemalloc as the global allocator for Pgcat. Windows is not officially supported by Pgcat but it should still compile but without Jemalloc as the allocator.

Author: drdrsh

Cargo.lock

@@ -34,3 +34,6 @@ rustls-pemfile = "1"
 hyper = { version = "0.14", features = ["full"] }
 phf = { version = "0.11.1", features = ["macros"] }
 exitcode = "1.1.2"
+
+[target.'cfg(not(target_env = "msvc"))'.dependencies]
+jemallocator = "0.3.2"

Cargo.toml

@@ -37,6 +37,13 @@ extern crate tokio;
 extern crate tokio_rustls;
 extern crate toml;
 
+#[cfg(not(target_env = "msvc"))]
+use jemallocator::Jemalloc;
+
+#[cfg(not(target_env = "msvc"))]
+#[global_allocator]
+static GLOBAL: Jemalloc = Jemalloc;
+
 use log::{error, info, warn};
 use parking_lot::Mutex;
 use pgcat::format_duration;