Hot-Reloading Refactor

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/alloc/je.rs

@@ -0,0 +1,52 @@
+use std::ffi::{c_char, c_void};
+
+use tikv_jemalloc_ctl as mallctl;
+use tikv_jemalloc_sys as ffi;
+use tikv_jemallocator as jemalloc;
+
+#[global_allocator]
+static JEMALLOC: jemalloc::Jemalloc = jemalloc::Jemalloc;
+
+#[must_use]
+pub fn memory_usage() -> String {
+	use mallctl::stats;
+	let allocated = stats::allocated::read().unwrap_or_default() as f64 / 1024.0 / 1024.0;
+	let active = stats::active::read().unwrap_or_default() as f64 / 1024.0 / 1024.0;
+	let mapped = stats::mapped::read().unwrap_or_default() as f64 / 1024.0 / 1024.0;
+	let metadata = stats::metadata::read().unwrap_or_default() as f64 / 1024.0 / 1024.0;
+	let resident = stats::resident::read().unwrap_or_default() as f64 / 1024.0 / 1024.0;
+	let retained = stats::retained::read().unwrap_or_default() as f64 / 1024.0 / 1024.0;
+	format!(
+		" allocated: {allocated:.2} MiB\n active: {active:.2} MiB\n mapped: {mapped:.2} MiB\n metadata: {metadata:.2} \
+		 MiB\n resident: {resident:.2} MiB\n retained: {retained:.2} MiB\n "
+	)
+}
+
+#[must_use]
+pub fn memory_stats() -> String {
+	const MAX_LENGTH: usize = 65536 - 4096;
+
+	let opts_s = "d";
+	let mut str = String::new();
+
+	let opaque = std::ptr::from_mut(&mut str).cast::<c_void>();
+	let opts_p: *const c_char = std::ffi::CString::new(opts_s).expect("cstring").into_raw() as *const c_char;
+
+	// SAFETY: calls malloc_stats_print() with our string instance which must remain
+	// in this frame. https://docs.rs/tikv-jemalloc-sys/latest/tikv_jemalloc_sys/fn.malloc_stats_print.html
+	unsafe { ffi::malloc_stats_print(Some(malloc_stats_cb), opaque, opts_p) };
+
+	str.truncate(MAX_LENGTH);
+	format!("<pre><code>{str}</code></pre>")
+}
+
+extern "C" fn malloc_stats_cb(opaque: *mut c_void, msg: *const c_char) {
+	// SAFETY: we have to trust the opaque points to our String
+	let res: &mut String = unsafe { opaque.cast::<String>().as_mut().unwrap() };
+
+	// SAFETY: we have to trust the string is null terminated.
+	let msg = unsafe { std::ffi::CStr::from_ptr(msg) };
+
+	let msg = String::from_utf8_lossy(msg.to_bytes());
+	res.push_str(msg.as_ref());
+}