Ledger purge printing (#15176)

ledger/src/blockstore/blockstore_purge.rs

@@ -1,4 +1,5 @@
 use super::*;
+use std::time::Instant;
 
 #[derive(Default)]
 pub struct PurgeStats {
@@ -47,6 +48,10 @@ impl Blockstore {
     ///
     /// Dangerous; Use with care
     pub fn purge_from_next_slots(&self, from_slot: Slot, to_slot: Slot) {
+        let mut count = 0;
+        let mut rewritten = 0;
+        let mut last_print = Instant::now();
+        let mut total_retain_us = 0;
         for (slot, mut meta) in self
             .slot_meta_iterator(0)
             .expect("unable to iterate over meta")
@@ -55,10 +60,23 @@ impl Blockstore {
                 break;
             }
 
+            count += 1;
+            if last_print.elapsed().as_millis() > 2000 {
+                info!(
+                    "purged: {} slots rewritten: {} retain_time: {}us",
+                    count, rewritten, total_retain_us
+                );
+                count = 0;
+                rewritten = 0;
+                total_retain_us = 0;
+                last_print = Instant::now();
+            }
+            let mut time = Measure::start("retain");
             let original_len = meta.next_slots.len();
             meta.next_slots
                 .retain(|slot| *slot < from_slot || *slot > to_slot);
             if meta.next_slots.len() != original_len {
+                rewritten += 1;
                 info!(
                     "purge_from_next_slots: meta for slot {} no longer refers to slots {:?}",
                     slot,
@@ -70,6 +88,8 @@ impl Blockstore {
                 )
                 .expect("couldn't update meta");
             }
+            time.stop();
+            total_retain_us += time.as_us();
         }
     }