[#1745] writecache: Set flush parameters based on max size

Signed-off-by: Evgenii Stratonikov <evgeniy@morphbits.ru>

pkg/local_object_storage/writecache/storage.go

@@ -20,6 +20,9 @@ import (
 // store represents persistent storage with in-memory LRU cache
 // for flushed items on top of it.
 type store struct {
+	maxFlushedMarksCount int
+	maxRemoveBatchSize   int
+
 	flushed simplelru.LRUCache
 	db      *bbolt.DB
 
@@ -27,11 +30,6 @@ type store struct {
 	fsKeysToRemove []string
 }
 
-const (
-	maxFlushedMarksCount = 256 * 1024 * 8
-	maxRemoveBatchSize   = maxFlushedMarksCount / 4
-)
-
 const dbName = "small.bolt"
 
 func (c *cache) openStore(readOnly bool) error {
@@ -70,7 +68,7 @@ func (c *cache) openStore(readOnly bool) error {
 	// Write-cache can be opened multiple times during `SetMode`.
 	// flushed map must not be re-created in this case.
 	if c.flushed == nil {
-		c.flushed, _ = lru.NewWithEvict(maxFlushedMarksCount, c.removeFlushed)
+		c.flushed, _ = lru.NewWithEvict(c.maxFlushedMarksCount, c.removeFlushed)
 	}
 	return nil
 }
@@ -87,7 +85,7 @@ func (c *cache) removeFlushed(key, value interface{}) {
 		c.fsKeysToRemove = append(c.fsKeysToRemove, key.(string))
 	}
 
-	if len(c.dbKeysToRemove)+len(c.fsKeysToRemove) >= maxRemoveBatchSize {
+	if len(c.dbKeysToRemove)+len(c.fsKeysToRemove) >= c.maxRemoveBatchSize {
 		c.dbKeysToRemove = c.deleteFromDB(c.dbKeysToRemove)
 		c.fsKeysToRemove = c.deleteFromDisk(c.fsKeysToRemove)
 	}

pkg/local_object_storage/writecache/writecache.go

@@ -97,6 +97,12 @@ func New(opts ...Option) Cache {
 		opts[i](&c.options)
 	}
 
+	// Make the LRU cache contain which take approximately 3/4 of the maximum space.
+	// Assume small and big objects are stored in 50-50 proportion.
+	c.maxFlushedMarksCount = int(c.maxCacheSize/c.maxObjectSize+c.maxCacheSize/c.smallObjectSize) / 2 * 3 / 4
+	// Trigger the removal when the cache is 7/8 full, so that new items can still arrive.
+	c.maxRemoveBatchSize = c.maxFlushedMarksCount / 8
+
 	return c
 }