v2.0: Cleanup PoH speed check error (backport of #2400) (#2458)

* Cleanup PoH speed check logs and error

The current logging and error message from the Poh speed check are
confusing. If the node fails, the error message states that the node is
too slow. But, the reported numbers are slot durations in nanoseconds
where a slower node will have a larger number. Lastly, the reported
numbers aren't labeled with a unit so it is hard to make sense of this
without looking at the actual code.

The check now computes and reports hashes per second.

(cherry picked from commit ecc05c5)

# Conflicts:
#	core/src/validator.rs

* merge conflicts

---------

Co-authored-by: steviez <steven@anza.xyz>

core/src/validator.rs

@@ -38,7 +38,7 @@ use {
         utils::{move_and_async_delete_path, move_and_async_delete_path_contents},
     },
     solana_client::connection_cache::{ConnectionCache, Protocol},
-    solana_entry::poh::compute_hash_time_ns,
+    solana_entry::poh::compute_hash_time,
     solana_geyser_plugin_manager::{
         geyser_plugin_service::GeyserPluginService, GeyserPluginManagerRequest,
     },
@@ -1676,24 +1676,23 @@ fn check_poh_speed(
     if let Some(hashes_per_tick) = genesis_config.hashes_per_tick() {
         let ticks_per_slot = genesis_config.ticks_per_slot();
         let hashes_per_slot = hashes_per_tick * ticks_per_slot;
-
         let hash_samples = maybe_hash_samples.unwrap_or(hashes_per_slot);
-        let hash_time_ns = compute_hash_time_ns(hash_samples);
-
-        let my_ns_per_slot = (hash_time_ns * hashes_per_slot) / hash_samples;
-        debug!("computed: ns_per_slot: {}", my_ns_per_slot);
-        let target_ns_per_slot = genesis_config.ns_per_slot() as u64;
-        debug!(
-            "cluster ns_per_hash: {}ns ns_per_slot: {}",
-            target_ns_per_slot / hashes_per_slot,
-            target_ns_per_slot
+
+        let hash_time = compute_hash_time(hash_samples);
+        let my_hashes_per_second = (hash_samples as f64 / hash_time.as_secs_f64()) as u64;
+        let target_slot_duration = Duration::from_nanos(genesis_config.ns_per_slot() as u64);
+        let target_hashes_per_second =
+            (hashes_per_slot as f64 / target_slot_duration.as_secs_f64()) as u64;
+
+        info!(
+            "PoH speed check: \
+            computed hashes per second {my_hashes_per_second}, \
+            target hashes per second {target_hashes_per_second}"
         );
-        if my_ns_per_slot < target_ns_per_slot {
-            let extra_ns = target_ns_per_slot - my_ns_per_slot;
-            info!("PoH speed check: Will sleep {}ns per slot.", extra_ns);
-        } else {
+        if my_hashes_per_second < target_hashes_per_second {
             return Err(format!(
-                "PoH is slower than cluster target tick rate! mine: {my_ns_per_slot} cluster: {target_ns_per_slot}.",
+                "PoH hashes/second rate is slower than the cluster target: \
+                mine {my_hashes_per_second}, cluster {target_hashes_per_second}"
             ));
         }
     }

entry/src/poh.rs

@@ -109,18 +109,18 @@ impl Poh {
     }
 }
 
-pub fn compute_hash_time_ns(hashes_sample_size: u64) -> u64 {
+pub fn compute_hash_time(hashes_sample_size: u64) -> Duration {
     info!("Running {} hashes...", hashes_sample_size);
     let mut v = Hash::default();
     let start = Instant::now();
     for _ in 0..hashes_sample_size {
         v = hash(v.as_ref());
     }
-    start.elapsed().as_nanos() as u64
+    start.elapsed()
 }
 
 pub fn compute_hashes_per_tick(duration: Duration, hashes_sample_size: u64) -> u64 {
-    let elapsed_ms = compute_hash_time_ns(hashes_sample_size) / (1000 * 1000);
+    let elapsed_ms = compute_hash_time(hashes_sample_size).as_millis() as u64;
     duration.as_millis() as u64 * hashes_sample_size / elapsed_ms
 }