Add Measure abstraction over measuring time intervals (#4851)

Allows one to swap in different implementations. This provides
the normal Insant::now() -> .elapsed() path.

measure/.gitignore

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+/target/

measure/Cargo.toml

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+[package]
+name = "solana-measure"
+description = "Blockchain, Rebuilt for Scale"
+version = "0.17.0"
+documentation = "https://docs.rs/solana"
+homepage = "https://solana.com/"
+readme = "../README.md"
+repository = "https://github.com/solana-labs/solana"
+authors = ["Solana Maintainers <maintainers@solana.com>"]
+license = "Apache-2.0"
+edition = "2018"
+
+[dependencies]
+solana-sdk = { path = "../sdk", version = "0.17.0" }

measure/src/lib.rs

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+pub mod measure;

measure/src/measure.rs

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+use solana_sdk::timing::duration_as_ns;
+use std::time::Instant;
+
+pub struct Measure {
+    start: Instant,
+    duration: u64,
+}
+
+impl Measure {
+    pub fn start(_name: &'static str) -> Self {
+        Self {
+            start: Instant::now(),
+            duration: 0,
+        }
+    }
+
+    pub fn stop(&mut self) {
+        self.duration = duration_as_ns(&self.start.elapsed());
+    }
+
+    pub fn as_us(&self) -> u64 {
+        self.duration / 1000
+    }
+
+    pub fn as_ms(&self) -> u64 {
+        self.duration / (1000 * 1000)
+    }
+
+    pub fn as_s(&self) -> f32 {
+        self.duration as f32 / (1000.0f32 * 1000.0f32 * 1000.0f32)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::thread::sleep;
+    use std::time::Duration;
+
+    #[test]
+    fn test_measure() {
+        let mut measure = Measure::start("test");
+        sleep(Duration::from_secs(1));
+        measure.stop();
+        assert!(measure.as_s() >= 0.99f32 && measure.as_s() <= 1.01f32);
+        assert!(measure.as_ms() >= 990 && measure.as_ms() <= 1_010);
+        assert!(measure.as_us() >= 999_000 && measure.as_us() <= 1_010_000);
+    }
+}