3 files changed, 110 insertions, 15 deletions

diff --git a/crates/ra_prof/src/lib.rs b/crates/ra_prof/src/lib.rs
index ba5609703..eb50965ae 100644
--- a/crates/ra_prof/src/lib.rs
+++ b/crates/ra_prof/src/lib.rs
@@ -1,5 +1,6 @@
 //! A collection of tools for profiling rust-analyzer.
 
+mod stop_watch;
 mod memory_usage;
 #[cfg(feature = "cpu_profiler")]
 mod google_cpu_profiler;
@@ -11,6 +12,7 @@ use std::cell::RefCell;
 pub use crate::{
     hprof::{init, init_from, profile},
     memory_usage::{Bytes, MemoryUsage},
+    stop_watch::{StopWatch, StopWatchSpan},
 };
 
 /// Prints backtrace to stderr, useful for debugging.
diff --git a/crates/ra_prof/src/memory_usage.rs b/crates/ra_prof/src/memory_usage.rs
index 745345fac..c2ecbd33c 100644
--- a/crates/ra_prof/src/memory_usage.rs
+++ b/crates/ra_prof/src/memory_usage.rs
@@ -3,9 +3,22 @@ use std::fmt;
 
 use cfg_if::cfg_if;
 
+#[derive(Copy, Clone)]
 pub struct MemoryUsage {
     pub allocated: Bytes,
-    pub resident: Bytes,
+}
+
+impl fmt::Display for MemoryUsage {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "{}", self.allocated)
+    }
+}
+
+impl std::ops::Sub for MemoryUsage {
+    type Output = MemoryUsage;
+    fn sub(self, rhs: MemoryUsage) -> MemoryUsage {
+        MemoryUsage { allocated: self.allocated - rhs.allocated }
+    }
 }
 
 impl MemoryUsage {
@@ -13,26 +26,20 @@ impl MemoryUsage {
         cfg_if! {
             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) }
+                let alloc = unsafe { libc::mallinfo() }.uordblks as isize;
+                MemoryUsage { allocated: Bytes(alloc) }
             } else {
-                MemoryUsage { allocated: Bytes(0), resident: Bytes(0) }
+                MemoryUsage { allocated: Bytes(0) }
             }
         }
     }
 }
 
-impl fmt::Display for MemoryUsage {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{} allocated {} resident", self.allocated, self.resident,)
-    }
-}
-
 #[derive(Default, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
-pub struct Bytes(usize);
+pub struct Bytes(isize);
 
 impl Bytes {
-    pub fn megabytes(self) -> usize {
+    pub fn megabytes(self) -> isize {
         self.0 / 1024 / 1024
     }
 }
@@ -42,10 +49,10 @@ impl fmt::Display for Bytes {
         let bytes = self.0;
         let mut value = bytes;
         let mut suffix = "b";
-        if value > 4096 {
+        if value.abs() > 4096 {
             value /= 1024;
             suffix = "kb";
-            if value > 4096 {
+            if value.abs() > 4096 {
                 value /= 1024;
                 suffix = "mb";
             }
@@ -56,7 +63,7 @@ impl fmt::Display for Bytes {
 
 impl std::ops::AddAssign<usize> for Bytes {
     fn add_assign(&mut self, x: usize) {
-        self.0 += x;
+        self.0 += x as isize;
     }
 }
 
diff --git a/crates/ra_prof/src/stop_watch.rs b/crates/ra_prof/src/stop_watch.rs
new file mode 100644
index 000000000..5e276190e
--- /dev/null
+++ b/crates/ra_prof/src/stop_watch.rs
@@ -0,0 +1,86 @@
+//! Like `std::time::Instant`, but also measures memory & CPU cycles.
+use std::{
+    fmt,
+    time::{Duration, Instant},
+};
+
+use crate::MemoryUsage;
+
+pub struct StopWatch {
+    time: Instant,
+    #[cfg(target_os = "linux")]
+    counter: Option<perf_event::Counter>,
+    memory: Option<MemoryUsage>,
+}
+
+pub struct StopWatchSpan {
+    pub time: Duration,
+    pub instructions: Option<u64>,
+    pub memory: Option<MemoryUsage>,
+}
+
+impl StopWatch {
+    pub fn start() -> StopWatch {
+        #[cfg(target_os = "linux")]
+        let counter = {
+            let mut counter = perf_event::Builder::new()
+                .build()
+                .map_err(|err| eprintln!("Failed to create perf counter: {}", err))
+                .ok();
+            if let Some(counter) = &mut counter {
+                if let Err(err) = counter.enable() {
+                    eprintln!("Failed to start perf counter: {}", err)
+                }
+            }
+            counter
+        };
+        let time = Instant::now();
+        StopWatch {
+            time,
+            #[cfg(target_os = "linux")]
+            counter,
+            memory: None,
+        }
+    }
+    pub fn memory(mut self, yes: bool) -> StopWatch {
+        if yes {
+            self.memory = Some(MemoryUsage::current());
+        }
+        self
+    }
+    pub fn elapsed(&mut self) -> StopWatchSpan {
+        let time = self.time.elapsed();
+
+        #[cfg(target_os = "linux")]
+        let instructions = self.counter.as_mut().and_then(|it| {
+            it.read().map_err(|err| eprintln!("Failed to read perf counter: {}", err)).ok()
+        });
+        #[cfg(not(target_os = "linux"))]
+        let instructions = None;
+
+        let memory = self.memory.map(|it| MemoryUsage::current() - it);
+        StopWatchSpan { time, instructions, memory }
+    }
+}
+
+impl fmt::Display for StopWatchSpan {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:.2?}", self.time)?;
+        if let Some(mut instructions) = self.instructions {
+            let mut prefix = "";
+            if instructions > 10000 {
+                instructions /= 1000;
+                prefix = "k"
+            }
+            if instructions > 10000 {
+                instructions /= 1000;
+                prefix = "m"
+            }
+            write!(f, ", {}{}i", instructions, prefix)?;
+        }
+        if let Some(memory) = self.memory {
+            write!(f, ", {}", memory)?;
+        }
+        Ok(())
+    }
+}