From 0b014090d245a3ac7b23dfaa6640ff3bd91cc512 Mon Sep 17 00:00:00 2001
From: Giulio Eulisse <10544+ktf@users.noreply.github.com>
Date: Thu, 3 Oct 2024 16:20:08 +0200
Subject: [PATCH] DPL Analysis: re-enable prefetching (#13559)

Now that ROOT supports prefetching with bulk reading, we can reenable this
which should cut in half the number of IOPS for the general case.
---
 Framework/Core/src/TableTreeHelpers.cxx | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/Framework/Core/src/TableTreeHelpers.cxx b/Framework/Core/src/TableTreeHelpers.cxx
index 14e4a43ea6cba..780126c89dd85 100644
--- a/Framework/Core/src/TableTreeHelpers.cxx
+++ b/Framework/Core/src/TableTreeHelpers.cxx
@@ -547,14 +547,14 @@ void TreeToTable::addAllColumns(TTree* tree, std::vector<std::string>&& names)
   if (mBranchReaders.empty()) {
     throw runtime_error("No columns will be read");
   }
-  //tree->SetCacheSize(50000000);
-  // FIXME: see https://github.com/root-project/root/issues/8962 and enable
-  // again once fixed.
-  //tree->SetClusterPrefetch(true);
-  //for (auto& reader : mBranchReaders) {
-  //  tree->AddBranchToCache(reader->branch());
-  //}
-  //tree->StopCacheLearningPhase();
+  // Was affected by https://github.com/root-project/root/issues/8962
+  // Re-enabling this seems to cut the number of IOPS in half
+  tree->SetCacheSize(25000000);
+  tree->SetClusterPrefetch(true);
+  for (auto& reader : mBranchReaders) {
+    tree->AddBranchToCache(reader->branch());
+  }
+  tree->StopCacheLearningPhase();
 }
 
 void TreeToTable::setLabel(const char* label)