Allow gathering memory stats on non-jemalloc Linux

Cargo.lock

@@ -1198,8 +1198,10 @@ name = "ra_prof"
 version = "0.1.0"
 dependencies = [
  "backtrace",
+ "cfg-if",
  "jemalloc-ctl",
  "jemallocator",
+ "libc",
  "mimalloc",
  "once_cell",
  "ra_arena",

crates/ra_prof/Cargo.toml

@@ -14,6 +14,8 @@ ra_arena = { path = "../ra_arena" }
 once_cell = "1.3.1"
 backtrace = { version = "0.3.44", optional = true }
 mimalloc = { version = "0.1.19", default-features = false, optional = true }
+cfg-if = "0.1.10"
+libc = "0.2.73"
 
 [target.'cfg(not(target_env = "msvc"))'.dependencies]
 jemallocator = { version = "0.3.2", optional = true }

crates/ra_prof/src/memory_usage.rs

@@ -1,5 +1,6 @@
 //! FIXME: write short doc here
 
+use cfg_if::cfg_if;
 use std::fmt;
 
 pub struct MemoryUsage {
@@ -8,20 +9,24 @@ pub struct MemoryUsage {
 }
 
 impl MemoryUsage {
-    #[cfg(all(feature = "jemalloc", not(target_env = "msvc")))]
     pub fn current() -> MemoryUsage {
+        cfg_if! {
+            if #[cfg(all(feature = "jemalloc", not(target_env = "msvc")))] {
                 jemalloc_ctl::epoch::advance().unwrap();
                 MemoryUsage {
                     allocated: Bytes(jemalloc_ctl::stats::allocated::read().unwrap()),
                     resident: Bytes(jemalloc_ctl::stats::resident::read().unwrap()),
                 }
-    }
-
-    #[cfg(any(not(feature = "jemalloc"), target_env = "msvc"))]
-    pub fn current() -> MemoryUsage {
+            } else if #[cfg(target_os = "linux")] {
+                // Note: This is incredibly slow.
+                let alloc = unsafe { libc::mallinfo() }.uordblks as u32 as usize;
+                MemoryUsage { allocated: Bytes(alloc), resident: Bytes(0) }
+            } else {
                 MemoryUsage { allocated: Bytes(0), resident: Bytes(0) }
             }
         }
+    }
+}
 
 impl fmt::Display for MemoryUsage {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {