From 07265d9787ba71fc6208ac01669d291b32765496 Mon Sep 17 00:00:00 2001
From: Alexey Shekhirin <a.shekhirin@gmail.com>
Date: Wed, 29 Nov 2023 08:47:47 +0000
Subject: [PATCH] perf(storage, mdbx): set rp augment limit (#5614)

---
 .../storage/db/src/implementation/mdbx/mod.rs | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/crates/storage/db/src/implementation/mdbx/mod.rs b/crates/storage/db/src/implementation/mdbx/mod.rs
index 3f6a5db88..91a56ca44 100644
--- a/crates/storage/db/src/implementation/mdbx/mod.rs
+++ b/crates/storage/db/src/implementation/mdbx/mod.rs
@@ -99,6 +99,32 @@ impl DatabaseEnv {
         });
         // configure more readers
         inner_env.set_max_readers(DEFAULT_MAX_READERS);
+        // This parameter sets the maximum size of the "reclaimed list", and the unit of measurement
+        // is "pages". Reclaimed list is the list of freed pages that's populated during the
+        // lifetime of DB transaction, and through which MDBX searches when it needs to insert new
+        // record with overflow pages. The flow is roughly the following:
+        // 0. We need to insert a record that requires N number of overflow pages (in consecutive
+        //    sequence inside the DB file).
+        // 1. Get some pages from the freelist, put them into the reclaimed list.
+        // 2. Search through the reclaimed list for the sequence of size N.
+        // 3. a. If found, return the sequence.
+        // 3. b. If not found, repeat steps 1-3. If the reclaimed list size is larger than
+        //    the `rp augment limit`, stop the search and allocate new pages at the end of the file:
+        //    https://github.com/paradigmxyz/reth/blob/2a4c78759178f66e30c8976ec5d243b53102fc9a/crates/storage/libmdbx-rs/mdbx-sys/libmdbx/mdbx.c#L11479-L11480.
+        //
+        // Basically, this parameter controls for how long do we search through the freelist before
+        // trying to allocate new pages. Smaller value will make MDBX to fallback to
+        // allocation faster, higher value will force MDBX to search through the freelist
+        // longer until the sequence of pages is found.
+        //
+        // The default value of this parameter is set depending on the DB size. The bigger the
+        // database, the larger is `rp augment limit`.
+        // https://github.com/paradigmxyz/reth/blob/2a4c78759178f66e30c8976ec5d243b53102fc9a/crates/storage/libmdbx-rs/mdbx-sys/libmdbx/mdbx.c#L10018-L10024.
+        //
+        // Previously, MDBX set this value as `256 * 1024` constant. Let's fallback to this,
+        // because we want to prioritize freelist lookup speed over database growth.
+        // https://github.com/paradigmxyz/reth/blob/fa2b9b685ed9787636d962f4366caf34a9186e66/crates/storage/libmdbx-rs/mdbx-sys/libmdbx/mdbx.c#L16017.
+        inner_env.set_rp_augment_limit(256 * 1024);
 
         if let Some(log_level) = log_level {
             // Levels higher than [LogLevel::Notice] require libmdbx built with `MDBX_DEBUG` option.