From 231e21ecc5b65ec18f3c4f761bcb8f3ac782bf9f Mon Sep 17 00:00:00 2001
From: John Spray <john@neon.tech>
Date: Thu, 18 Jul 2024 09:48:40 +0000
Subject: [PATCH] use image compression for image values in delta layers

---
 .../src/tenant/storage_layer/delta_layer.rs   | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/pageserver/src/tenant/storage_layer/delta_layer.rs b/pageserver/src/tenant/storage_layer/delta_layer.rs
index 43941b6e17..6026db3c1d 100644
--- a/pageserver/src/tenant/storage_layer/delta_layer.rs
+++ b/pageserver/src/tenant/storage_layer/delta_layer.rs
@@ -457,8 +457,15 @@ impl DeltaLayerWriterInner {
         ctx: &RequestContext,
     ) -> (Vec<u8>, anyhow::Result<()>) {
         assert!(self.lsn_range.start <= lsn);
-        // We don't want to use compression in delta layer creation
-        let compression = ImageCompressionAlgorithm::Disabled;
+
+        let compression = if val.len() >= 8192 {
+            // For full page images, respect configured image compression algorithm.
+            self.conf.image_compression
+        } else {
+            // For small writes, do not use compression.  Compression ratios on tiny buffers do not justify CPU cost.
+            ImageCompressionAlgorithm::Disabled
+        };
+
         let (val, res) = self
             .blob_writer
             .write_blob_maybe_compressed(val, ctx, compression)
@@ -479,6 +486,10 @@ impl DeltaLayerWriterInner {
         self.blob_writer.size() + self.tree.borrow_writer().size()
     }
 
+    fn size_values(&self) -> u64 {
+        self.blob_writer.size()
+    }
+
     ///
     /// Finish writing the delta layer.
     ///
@@ -668,6 +679,10 @@ impl DeltaLayerWriter {
         self.inner.as_ref().unwrap().size()
     }
 
+    pub fn size_values(&self) -> u64 {
+        self.inner.as_ref().unwrap().size_values()
+    }
+
     ///
     /// Finish writing the delta layer.
     ///