From b1f0bbd12afe7efd8e151acf959c9ca51189dc3f Mon Sep 17 00:00:00 2001
From: Alex Chi Z <chi@neon.tech>
Date: Wed, 28 Jun 2023 15:38:14 -0400
Subject: [PATCH] add reduce num sorted run trigger

Signed-off-by: Alex Chi Z <chi@neon.tech>
---
 pageserver/src/tenant/timeline.rs | 57 +++++++++++++++++++++++--------
 1 file changed, 43 insertions(+), 14 deletions(-)

diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 028e9e0e28..647805bd03 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -3859,8 +3859,9 @@ impl Timeline {
         tier_sizes: Vec<(usize, u64)>,
     ) -> Option<Vec<usize>> {
         let size_ratio = 1.25;
-        let space_amplification_ratio = 2.0;
-        let max_merge_width = 20;
+        let space_amplification_ratio = 1.5;
+        let max_merge_width = 10;
+        let min_merge_width = 3;
 
         // Trigger 1: by space amplification, do full compaction
         let total_tier_size = tier_sizes.iter().map(|(_, size)| *size).sum::<u64>();
@@ -3868,7 +3869,10 @@ impl Timeline {
         let estimated_space_amp = (total_tier_size - last_tier_size) as f64 / last_tier_size as f64;
         if estimated_space_amp > space_amplification_ratio {
             if !skip_tiers.is_empty() {
-                info!("full compaction cannot be triggered as some layers are being compacted: {:?}", skip_tiers);
+                info!(
+                    "full compaction cannot be triggered as some layers are being compacted: {:?}",
+                    skip_tiers
+                );
             } else {
                 info!("full compaction triggered by space amplification");
                 let tiers = tier_sizes
@@ -3878,14 +3882,16 @@ impl Timeline {
                     .rev()
                     .map(|(tier_id, _)| *tier_id)
                     .collect::<Vec<_>>();
-                return Some(tiers);
+                if tiers.len() >= min_merge_width {
+                    return Some(tiers);
+                }
             }
         }
 
         // Trigger 2: by size ratio
         let mut total_size_up_to_lvl = 0;
         let mut compact_tiers = Vec::new();
-        for (tier_id, size) in tier_sizes {
+        for &(tier_id, size) in &tier_sizes {
             if total_size_up_to_lvl != 0 && size as f64 / total_size_up_to_lvl as f64 > size_ratio {
                 info!("compaction triggered by size ratio");
                 let compact_tiers = compact_tiers
@@ -3895,7 +3901,11 @@ impl Timeline {
                     .rev()
                     .copied()
                     .collect_vec();
-                return Some(compact_tiers);
+                if compact_tiers.len() >= min_merge_width {
+                    return Some(compact_tiers);
+                } else {
+                    break;
+                }
             }
             if skip_tiers.contains(&tier_id) {
                 break;
@@ -3903,7 +3913,30 @@ impl Timeline {
             total_size_up_to_lvl += size;
             compact_tiers.push(tier_id);
         }
-        None
+
+        // Trigger 3: reduce number of sorted runs, pick up to max_merge_width files to compact.
+        let mut compact_tiers = Vec::new();
+        for (tier_id, size) in tier_sizes {
+            if skip_tiers.contains(&tier_id) {
+                break;
+            }
+            total_size_up_to_lvl += size;
+            compact_tiers.push(tier_id);
+        }
+
+        info!("compaction triggered by reducing sorted runs");
+        let compact_tiers = compact_tiers
+            .iter()
+            .rev()
+            .take(max_merge_width)
+            .rev()
+            .copied()
+            .collect_vec();
+        if compact_tiers.len() >= min_merge_width {
+            return Some(compact_tiers);
+        } else {
+            return None;
+        }
     }
 
     async fn compact_tiered_phase1(
@@ -3940,12 +3973,6 @@ impl Timeline {
                 return Ok(None);
             };
 
-            let min_merge_width = 3;
-
-            if tier_to_compact.len() < min_merge_width {
-                return Ok(None);
-            }
-
             println!("tier_to_compact: {tier_to_compact:?}");
             for &tier in &tier_to_compact {
                 compacting_tiers.insert(tier);
@@ -4318,7 +4345,9 @@ impl Timeline {
             compacting_tiers.remove(&tier);
         }
 
-        info!("compaction complete, removed_tiers = {removed_tiers:?}, new_tier_at = {new_tier_at}");
+        info!(
+            "compaction complete, removed_tiers = {removed_tiers:?}, new_tier_at = {new_tier_at}"
+        );
 
         drop_wlock(guard);