Add support for differential flame graphs

.gitignore

@@ -3,3 +3,4 @@
 /perf*
 *.log
 /*.svg
+.DS_Store

src/bin/flamegraph.rs

@@ -40,36 +40,33 @@ struct Opt {
     /// use consistent palette (palette.map)
     #[structopt(long = "cp")]
     cp: bool,
+
+    /// switch differential hues (green<->red)
+    #[structopt(long = "negate")]
+    negate: bool,
 }
 
 impl Into<Options> for Opt {
     fn into(self) -> Options {
-        let func_frameattrs = match self.nameattr_file {
-            Some(file) => match FuncFrameAttrsMap::from_file(&file) {
-                Ok(n) => n,
+        let mut options = Options::default();
+        options.colors = self.colors;
+        options.bgcolors = self.bgcolors;
+        options.hash = self.hash;
+        options.consistent_palette = self.cp;
+        if let Some(file) = self.nameattr_file {
+            match FuncFrameAttrsMap::from_file(&file) {
+                Ok(m) => {
+                    options.func_frameattrs = m;
+                }
                 Err(e) => panic!("Error reading {}: {:?}", file.display(), e),
-            },
-            None => FuncFrameAttrsMap::default(),
-        };
-        let direction = if self.inverted {
-            Direction::Inverted
-        } else {
-            Direction::Straight
-        };
-        let title = if self.inverted {
-            "Icicle Graph".to_string()
-        } else {
-            "Flame Graph".to_string()
+            }
         };
-        Options {
-            colors: self.colors,
-            bgcolors: self.bgcolors,
-            hash: self.hash,
-            consistent_palette: self.cp,
-            func_frameattrs,
-            direction,
-            title,
+        if self.inverted {
+            options.direction = Direction::Inverted;
+            options.title = "Icicle Graph".to_string();
         }
+        options.negate_differentials = self.negate;
+        options
     }
 }
 

src/flamegraph/color/mod.rs

@@ -255,6 +255,22 @@ pub(super) fn color(
     rgb_components_for_palette(palette, name, v1, v2, v3)
 }
 
+pub(super) fn color_scale(value: isize, max: usize) -> (u8, u8, u8) {
+    if value == 0 {
+        (255, 255, 255)
+    } else if value > 0 {
+        // A positive value indicates _more_ samples,
+        // and hence more time spent, so we give it a red hue.
+        let c = (210 * (max as isize - value) / max as isize) as u8;
+        (255, c, c)
+    } else {
+        // A negative value indicates _fewer_ samples,
+        // or a speed-up, so we give it a green hue.
+        let c = (210 * (max as isize + value) / max as isize) as u8;
+        (c, c, 255)
+    }
+}
+
 fn default_bg_color_for(palette: Palette) -> BackgroundColor {
     match palette {
         Palette::Basic(BasicPalette::Mem) => BackgroundColor::Green,

src/flamegraph/merge.rs

@@ -12,14 +12,22 @@ pub(super) struct TimedFrame<'a> {
     pub(super) location: Frame<'a>,
     pub(super) start_time: usize,
     pub(super) end_time: usize,
+    pub(super) delta: Option<isize>,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub(super) struct FrameTime {
+    pub(super) start_time: usize,
+    pub(super) delta: Option<isize>,
 }
 
 fn flow<'a, LI, TI>(
-    tmp: &mut HashMap<Frame<'a>, usize>,
+    tmp: &mut HashMap<Frame<'a>, FrameTime>,
     frames: &mut Vec<TimedFrame<'a>>,
     last: LI,
     this: TI,
     time: usize,
+    delta: Option<isize>,
 ) where
     LI: IntoIterator<Item = &'a str>,
     TI: IntoIterator<Item = &'a str>,
@@ -50,31 +58,50 @@ fn flow<'a, LI, TI>(
         };
 
         //eprintln!("at {} ending frame {:?}", time, key);
-        let start_time = tmp.remove(&key).unwrap_or_else(|| {
+        let frame_time = tmp.remove(&key).unwrap_or_else(|| {
             unreachable!("did not have start time for {:?}", key);
         });
 
-        let key = TimedFrame {
+        let frame = TimedFrame {
             location: key,
-            start_time,
+            start_time: frame_time.start_time,
             end_time: time,
+            delta: frame_time.delta,
         };
-        frames.push(key);
+        frames.push(frame);
     }
 
-    for (i, func) in this.enumerate() {
+    let mut i = 0;
+    while this.peek().is_some() {
+        let func = this.next().unwrap();
         let key = Frame {
             function: func,
             depth: shared_depth + i,
         };
+
+        let is_last = this.peek().is_none();
+        let delta = match delta {
+            Some(_) if !is_last => Some(0),
+            d => d,
+        };
+        let frame_time = FrameTime {
+            start_time: time,
+            delta,
+        };
+
         //eprintln!("stored tmp for time {}: {:?}", time, key);
-        if let Some(start_time) = tmp.insert(key, time) {
-            unreachable!("start time {} already registered for frame", start_time);
+        if let Some(frame_time) = tmp.insert(key, frame_time) {
+            unreachable!(
+                "start time {} already registered for frame",
+                frame_time.start_time
+            );
         }
+
+        i += 1;
     }
 }
 
-pub(super) fn frames<'a, I>(lines: I) -> (Vec<TimedFrame<'a>>, usize, usize)
+pub(super) fn frames<'a, I>(lines: I) -> (Vec<TimedFrame<'a>>, usize, usize, usize)
 where
     I: IntoIterator<Item = &'a str>,
 {
@@ -83,34 +110,30 @@ where
     let mut last = "";
     let mut tmp = Default::default();
     let mut frames = Default::default();
+    let mut delta = None;
+    let mut delta_max = 1;
     for line in lines {
         let mut line = line.trim();
         if line.is_empty() {
             continue;
         }
 
-        let nsamples = if let Some(samplesi) = line.rfind(' ') {
-            let mut samples = &line[(samplesi + 1)..];
-            // strip fractional part (if any);
-            // foobar 1.klwdjlakdj
-            if let Some(doti) = samples.find('.') {
-                samples = &samples[..doti];
-            }
-            match samples.parse::<usize>() {
-                Ok(nsamples) => {
-                    // remove nsamples part we just parsed from line
-                    line = line[..samplesi].trim_end();
-                    // give out the sample count
-                    nsamples
-                }
-                Err(_) => {
-                    ignored += 1;
-                    continue;
+        // Usually there will only be one samples column at the end of a line,
+        // but for differentials there will be two. In the case there are two
+        // we compute the delta between them and use the second one as as the
+        // number of samples for this frame.
+        let nsamples = match (parse_nsamples(&mut line), parse_nsamples(&mut line)) {
+            (Some(s2), nsamples1) => {
+                delta = nsamples1.and_then(|s1| Some(s2 as isize - s1 as isize));
+                if let Some(delta) = delta {
+                    delta_max = std::cmp::max(delta.abs() as usize, delta_max);
                 }
+                s2
+            }
+            _ => {
+                ignored += 1;
+                continue;
             }
-        } else {
-            ignored += 1;
-            continue;
         };
 
         if line.is_empty() {
@@ -124,7 +147,7 @@ where
         if last.is_empty() {
             // need to special-case this, because otherwise iter("") + "".split(';') == ["", ""]
             //eprintln!("flow(_, {}, {})", stack, time);
-            flow(&mut tmp, &mut frames, None, this, time);
+            flow(&mut tmp, &mut frames, None, this, time, delta);
         } else {
             //eprintln!("flow({}, {}, {})", last, stack, time);
             flow(
@@ -133,6 +156,7 @@ where
                 iter::once("").chain(last.split(';')),
                 this,
                 time,
+                delta,
             );
         }
 
@@ -148,8 +172,26 @@ where
             iter::once("").chain(last.split(';')),
             None,
             time,
+            delta,
         );
     }
 
-    (frames, time, ignored)
+    (frames, time, ignored, delta_max)
+}
+
+// Parse and remove the number of samples from the end of a line.
+fn parse_nsamples(line: &mut &str) -> Option<usize> {
+    let samplesi = line.rfind(' ')?;
+    let mut samples = &line[(samplesi + 1)..];
+    // strip fractional part (if any);
+    // foobar 1.klwdjlakdj
+    // TODO: Properly handle fractional samples (see issue #43)
+    if let Some(doti) = samples.find('.') {
+        samples = &samples[..doti];
+    }
+
+    let nsamples = samples.parse::<usize>().ok()?;
+    // remove nsamples part we just parsed from line
+    *line = line[..samplesi].trim_end();
+    Some(nsamples)
 }

src/flamegraph/mod.rs

@@ -32,7 +32,7 @@ const XPAD: usize = 10; // pad lefm and right
 const FRAMEPAD: usize = 1; // vertical padding for frames
 const PALETTE_FILE: &str = "palette.map";
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct Options {
     pub colors: color::Palette,
     pub bgcolors: Option<color::BackgroundColor>,
@@ -41,6 +41,22 @@ pub struct Options {
     pub func_frameattrs: FuncFrameAttrsMap,
     pub direction: Direction,
     pub title: String,
+    pub negate_differentials: bool,
+}
+
+impl Default for Options {
+    fn default() -> Self {
+        Options {
+            colors: Default::default(),
+            bgcolors: Default::default(),
+            hash: Default::default(),
+            consistent_palette: Default::default(),
+            func_frameattrs: Default::default(),
+            direction: Default::default(),
+            title: "Flame Graph".to_string(),
+            negate_differentials: Default::default(),
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
@@ -156,7 +172,7 @@ where
     let (bgcolor1, bgcolor2) = color::bgcolor_for(opt.bgcolors, opt.colors);
 
     let mut buffer = StrStack::new();
-    let (mut frames, time, ignored) = merge::frames(lines);
+    let (mut frames, time, ignored, delta_max) = merge::frames(lines);
     if ignored != 0 {
         warn!("Ignored {} lines with invalid format", ignored);
     }
@@ -254,15 +270,37 @@ where
             write!(buffer, "all ({} samples, 100%)", samples_txt)
         } else {
             let pct = (100 * samples) as f64 / timemax as f64;
-
-            // strip any annotation
-            write!(
-                buffer,
-                "{} ({} samples, {:.2}%)",
-                deannotate(&frame.location.function),
-                samples_txt,
-                pct
-            )
+            match frame.delta {
+                None => write!(
+                    buffer,
+                    "{} ({} samples, {:.2}%)",
+                    deannotate(&frame.location.function),
+                    samples_txt,
+                    pct
+                ),
+                // Special case delta == 0 so we don't format percentage with a + sign.
+                Some(delta) if delta == 0 => write!(
+                    buffer,
+                    "{} ({} samples, {:.2}%; 0.00%)",
+                    deannotate(&frame.location.function),
+                    samples_txt,
+                    pct,
+                ),
+                Some(mut delta) => {
+                    if opt.negate_differentials {
+                        delta = -delta;
+                    }
+                    let delta_pct = (100 * delta) as f64 / timemax as f64;
+                    write!(
+                        buffer,
+                        "{} ({} samples, {:.2}%; {:+.2}%)",
+                        deannotate(&frame.location.function),
+                        samples_txt,
+                        pct,
+                        delta_pct
+                    )
+                }
+            }
         };
 
         let frame_attributes = opt
@@ -325,6 +363,11 @@ where
             color::VDGREY
         } else if frame.location.function == "-" {
             color::DGREY
+        } else if let Some(mut delta) = frame.delta {
+            if opt.negate_differentials {
+                delta = -delta;
+            }
+            color::color_scale(delta, delta_max)
         } else if let Some(ref mut palette_map) = palette_map {
             palette_map.find_color_for(&frame.location.function, |name| {
                 color::color(opt.colors, opt.hash, name, &mut thread_rng)