From a0eafa12e315ca3cfbb5fa7701c43dcf0cb8b4b4 Mon Sep 17 00:00:00 2001
From: Pankaj Garg <pankaj@solana.com>
Date: Mon, 2 Dec 2019 18:02:11 -0800
Subject: [PATCH] Update to hashes_per_tick computation, and tick duration
 datapoint (#7127)

---
 core/src/poh_service.rs | 14 ++++++++++++++
 ledger/src/poh.rs       | 31 +++++++------------------------
 2 files changed, 21 insertions(+), 24 deletions(-)

diff --git a/core/src/poh_service.rs b/core/src/poh_service.rs
index aa82a1a1b..10136ef80 100644
--- a/core/src/poh_service.rs
+++ b/core/src/poh_service.rs
@@ -2,11 +2,13 @@
 //! "ticks", a measure of time in the PoH stream
 use crate::poh_recorder::PohRecorder;
 use core_affinity;
+use solana_sdk::clock::DEFAULT_TICKS_PER_SLOT;
 use solana_sdk::poh_config::PohConfig;
 use solana_sys_tuner;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::thread::{self, sleep, Builder, JoinHandle};
+use std::time::Instant;
 
 pub struct PohService {
     tick_producer: JoinHandle<()>,
@@ -87,10 +89,22 @@ impl PohService {
 
     fn tick_producer(poh_recorder: Arc<Mutex<PohRecorder>>, poh_exit: &AtomicBool) {
         let poh = poh_recorder.lock().unwrap().poh.clone();
+        let mut now = Instant::now();
+        let mut num_ticks = 0;
         loop {
             if poh.lock().unwrap().hash(NUM_HASHES_PER_BATCH) {
                 // Lock PohRecorder only for the final hash...
                 poh_recorder.lock().unwrap().tick();
+                num_ticks += 1;
+                if num_ticks >= DEFAULT_TICKS_PER_SLOT * 2 {
+                    datapoint_debug!(
+                        "poh-service",
+                        ("ticks", num_ticks as i64, i64),
+                        ("elapsed_ms", now.elapsed().as_millis() as i64, i64),
+                    );
+                    num_ticks = 0;
+                    now = Instant::now();
+                }
                 if poh_exit.load(Ordering::Relaxed) {
                     break;
                 }
diff --git a/ledger/src/poh.rs b/ledger/src/poh.rs
index bce402013..eaf075473 100644
--- a/ledger/src/poh.rs
+++ b/ledger/src/poh.rs
@@ -1,7 +1,6 @@
 //! The `Poh` module provides an object for generating a Proof of History.
 use log::*;
 use solana_sdk::hash::{hash, hashv, Hash};
-use std::thread::{Builder, JoinHandle};
 use std::time::{Duration, Instant};
 
 pub struct Poh {
@@ -84,34 +83,18 @@ impl Poh {
 }
 
 pub fn compute_hashes_per_tick(duration: Duration, hashes_sample_size: u64) -> u64 {
-    let num_cpu = sys_info::cpu_num().unwrap();
     // calculate hash rate with the system under maximum load
     info!(
         "Running {} hashes in parallel on all threads...",
         hashes_sample_size
     );
-    let threads: Vec<JoinHandle<u64>> = (0..num_cpu)
-        .map(|_| {
-            Builder::new()
-                .name("solana-poh".to_string())
-                .spawn(move || {
-                    let mut v = Hash::default();
-                    let start = Instant::now();
-                    for _ in 0..hashes_sample_size {
-                        v = hash(&v.as_ref());
-                    }
-                    start.elapsed().as_millis() as u64
-                })
-                .unwrap()
-        })
-        .collect();
-
-    let avg_elapsed = (threads
-        .into_iter()
-        .map(|elapsed| elapsed.join().unwrap())
-        .sum::<u64>())
-        / u64::from(num_cpu);
-    duration.as_millis() as u64 * hashes_sample_size / avg_elapsed
+    let mut v = Hash::default();
+    let start = Instant::now();
+    for _ in 0..hashes_sample_size {
+        v = hash(&v.as_ref());
+    }
+    let elapsed = start.elapsed().as_millis() as u64;
+    duration.as_millis() as u64 * hashes_sample_size / elapsed
 }
 
 #[cfg(test)]