Update metrics tracking and enhance cache eviction strategies

- Added metrics for bytes saved from cache to improve performance insights.
- Updated cache eviction strategies in MemoryFS and DiskFS to include metrics tracking for hits and evictions.
- Enhanced README.md with updated garbage collection algorithm descriptions and recommendations for cache usage.
- Introduced new madviseSequential functionality for improved memory access hints on Unix systems.
- Adjusted validation configuration in examples to better reflect realistic usage scenarios.

vfs/memory/memory.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"s1d3sw1ped/steamcache2/steamcache/metrics"
 	"s1d3sw1ped/steamcache2/vfs"
 	"s1d3sw1ped/steamcache2/vfs/locks"
 	"s1d3sw1ped/steamcache2/vfs/lru"
@@ -33,6 +34,7 @@ type MemoryFS struct {
 	keyLocks    []sync.Map // Sharded lock pools for better concurrency
 	LRU         *lru.LRUList[*types.FileInfo]
 	timeUpdater *types.BatchedTimeUpdate // Batched time updates for better performance
+	metrics     *metrics.Metrics
 }
 
 // New creates a new MemoryFS
@@ -55,6 +57,12 @@ func New(capacity int64) (*MemoryFS, error) {
 	}, nil
 }
 
+// SetMetrics allows the owner (SteamCache) to inject the metrics collector
+// so that per-tier hit and eviction counters can be recorded.
+func (m *MemoryFS) SetMetrics(met *metrics.Metrics) {
+	m.metrics = met
+}
+
 // Name returns the name of this VFS
 func (m *MemoryFS) Name() string {
 	return "MemoryFS"
@@ -209,6 +217,10 @@ func (m *MemoryFS) Open(key string) (io.ReadCloser, error) {
 	// Use zero-copy approach - return reader that reads directly from buffer
 	m.mu.Unlock()
 
+	if m.metrics != nil {
+		m.metrics.IncrementMemoryCacheHits()
+	}
+
 	return &memoryReadCloser{
 		buffer: buffer,
 		offset: 0,
@@ -344,6 +356,10 @@ func (m *MemoryFS) EvictLRU(bytesNeeded uint) uint {
 		}
 	}
 	m.mu.Unlock()
+
+	if m.metrics != nil && evicted > 0 {
+		m.metrics.IncrementEvictions()
+	}
 	return evicted
 }
 
@@ -395,6 +411,10 @@ func (m *MemoryFS) EvictBySize(bytesNeeded uint, ascending bool) uint {
 		}
 	}
 	m.mu.Unlock()
+
+	if m.metrics != nil && evicted > 0 {
+		m.metrics.IncrementEvictions()
+	}
 	return evicted
 }
 
@@ -442,6 +462,10 @@ func (m *MemoryFS) EvictFIFO(bytesNeeded uint) uint {
 		}
 	}
 	m.mu.Unlock()
+
+	if m.metrics != nil && evicted > 0 {
+		m.metrics.IncrementEvictions()
+	}
 	return evicted
 }
 
@@ -494,6 +518,10 @@ func (m *MemoryFS) EvictLFU(bytesNeeded uint) uint {
 		}
 	}
 	m.mu.Unlock()
+
+	if m.metrics != nil && evicted > 0 {
+		m.metrics.IncrementEvictions()
+	}
 	return evicted
 }
 
@@ -548,5 +576,9 @@ func (m *MemoryFS) EvictHybrid(bytesNeeded uint) uint {
 		}
 	}
 	m.mu.Unlock()
+
+	if m.metrics != nil && evicted > 0 {
+		m.metrics.IncrementEvictions()
+	}
 	return evicted
 }