From 3ecdceceee909b57faa70ac7efa4ff58245b35d0 Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Tue, 1 Apr 2025 17:29:56 +0200
Subject: reduce disk io during gc (#335)

* do cache bucket flush/write snapshot as part of compact to reduce disk I/O
---
 src/zenstore/cache/cachedisklayer.cpp | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

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

diff --git a/src/zenstore/cache/cachedisklayer.cpp b/src/zenstore/cache/cachedisklayer.cpp
index b2d2416be..e4d962b56 100644
--- a/src/zenstore/cache/cachedisklayer.cpp
+++ b/src/zenstore/cache/cachedisklayer.cpp
@@ -2731,9 +2731,10 @@ class DiskBucketStoreCompactor : public GcStoreCompactor
 	using CacheBucket	= ZenCacheDiskLayer::CacheBucket;
 
 public:
-	DiskBucketStoreCompactor(CacheBucket& Bucket, std::vector<std::pair<IoHash, uint64_t>>&& ExpiredStandaloneKeys)
+	DiskBucketStoreCompactor(CacheBucket& Bucket, std::vector<std::pair<IoHash, uint64_t>>&& ExpiredStandaloneKeys, bool FlushBucket)
 	: m_Bucket(Bucket)
 	, m_ExpiredStandaloneKeys(std::move(ExpiredStandaloneKeys))
+	, m_FlushBucket(FlushBucket)
 	{
 		m_ExpiredStandaloneKeys.shrink_to_fit();
 	}
@@ -2960,6 +2961,10 @@ public:
 				}
 			}
 		}
+		if (m_FlushBucket)
+		{
+			m_Bucket.Flush();
+		}
 	}
 
 	virtual std::string GetGcName(GcCtx& Ctx) override { return m_Bucket.GetGcName(Ctx); }
@@ -2967,6 +2972,7 @@ public:
 private:
 	ZenCacheDiskLayer::CacheBucket&			 m_Bucket;
 	std::vector<std::pair<IoHash, uint64_t>> m_ExpiredStandaloneKeys;
+	bool									 m_FlushBucket = false;
 };
 
 GcStoreCompactor*
@@ -2990,24 +2996,6 @@ ZenCacheDiskLayer::CacheBucket::RemoveExpiredData(GcCtx& Ctx, GcStats& Stats)
 					 NiceBytes(Stats.FreedMemory),
 					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
 		}
-		if (Stats.DeletedCount > 0)
-		{
-			bool Expected = false;
-			if (m_IsFlushing || !m_IsFlushing.compare_exchange_strong(Expected, true))
-			{
-				return;
-			}
-			auto FlushingGuard = MakeGuard([&] { m_IsFlushing.store(false); });
-
-			try
-			{
-				SaveSnapshot([]() { return 0; });
-			}
-			catch (const std::exception& Ex)
-			{
-				ZEN_WARN("Failed to write index and manifest after RemoveExpiredData in '{}'. Reason: '{}'", m_BucketDir, Ex.what());
-			}
-		}
 	});
 
 	const GcClock::Tick ExpireTicks = Ctx.Settings.CacheExpireTime.time_since_epoch().count();
@@ -3094,7 +3082,7 @@ ZenCacheDiskLayer::CacheBucket::RemoveExpiredData(GcCtx& Ctx, GcStats& Stats)
 		return nullptr;
 	}
 
-	return new DiskBucketStoreCompactor(*this, std::move(ExpiredStandaloneKeys));
+	return new DiskBucketStoreCompactor(*this, std::move(ExpiredStandaloneKeys), /*FlushBucket*/ Stats.DeletedCount > 0);
 }
 
 bool
-- 
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