From 387b6d99e6ef3958a6fd78b22c48bb8a85b53bda Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Wed, 4 Oct 2023 14:37:49 +0200
Subject: refactor comapactcas index (#443)

- Bugfix: Fix scrub messing up payload and access time in disk cache bucket when compacting index
- Improvement: Split up disk cache bucket index into hash lookup and payload array to improve performance
- Improvement: Reserve space up front for compact binary output when saving cache bucket manifest to improve performance
---
 src/zenserver/cache/cachedisklayer.cpp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

(limited to 'src/zenserver/cache/cachedisklayer.cpp')

diff --git a/src/zenserver/cache/cachedisklayer.cpp b/src/zenserver/cache/cachedisklayer.cpp
index 9883e2119..7ce713de9 100644
--- a/src/zenserver/cache/cachedisklayer.cpp
+++ b/src/zenserver/cache/cachedisklayer.cpp
@@ -884,7 +884,14 @@ ZenCacheDiskLayer::CacheBucket::MakeManifest(IndexMap&& Index, std::vector<Acces
 
 	ZEN_TRACE_CPU("Z$::Disk::Bucket::MakeManifest");
 
-	CbObjectWriter Writer;
+	size_t ItemCount = m_Index.size();
+
+	// This tends to overestimate a little bit but it is still way more accurate than what we get with exponential growth
+	// And we don't need to reallocate theunderying buffer in almost every case
+	const size_t   EstimatedSizePerItem = 54u;
+	const size_t   ReserveSize			= ItemCount == 0 ? 48u : RoundUp(32u + (ItemCount * EstimatedSizePerItem), 128);
+	CbObjectWriter Writer(ReserveSize);
+
 	Writer << "BucketId"sv << m_BucketId;
 	Writer << "Version"sv << CurrentDiskBucketVersion;
 
@@ -1213,8 +1220,8 @@ ZenCacheDiskLayer::CacheBucket::ScrubStorage(ScrubContext& Ctx)
 					for (auto It : m_Index)
 					{
 						size_t EntryIndex = Payloads.size();
-						Payloads.push_back(m_Payloads[EntryIndex]);
-						AccessTimes.push_back(m_AccessTimes[EntryIndex]);
+						Payloads.push_back(m_Payloads[It.second]);
+						AccessTimes.push_back(m_AccessTimes[It.second]);
 						Index.insert({It.first, EntryIndex});
 					}
 					m_Index.swap(Index);
-- 
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