mount: size the directory listing cache with -dirListCacheEntries

Defaults to 200k children, a few tens of megabytes, which covers one very
wide directory. Zero disables it. Least recently used directories are
dropped to stay inside the budget.

A subscription gap means the mount cannot know what it missed, so the
resubscribe path drops every cached listing along with the cached-ness
flags it already resets.

weed/command/mount.go

@@ -3,6 +3,8 @@ package command
 import (
 	"os"
 	"time"
+
+	"github.com/seaweedfs/seaweedfs/weed/mount/meta_cache"
 )
 
 type MountOptions struct {
@@ -20,6 +22,7 @@ type MountOptions struct {
 	concurrentWriters    *int
 	concurrentReaders    *int
 	cacheMetaTtlSec      *int
+	dirListCacheEntries  *int
 	cacheDirForRead      *string
 	cacheDirForWrite     *string
 	cacheSizeMBForRead   *int64
@@ -114,6 +117,7 @@ func init() {
 	mountOptions.cacheDirForWrite = cmdMount.Flag.String("cacheDirWrite", "", "buffer writes mostly for large files")
 	mountOptions.writeBufferSizeMB = cmdMount.Flag.Int64("writeBufferSizeMB", 0, "global cap on the per-mount write buffer (memory + swap) in MB, 0 means unlimited. Bounds /tmp growth when volume uploads stall")
 	mountOptions.cacheMetaTtlSec = cmdMount.Flag.Int("cacheMetaTtlSec", 60, "metadata cache validity seconds")
+	mountOptions.dirListCacheEntries = cmdMount.Flag.Int("dirListCacheEntries", meta_cache.DefaultListingCacheEntries, "directory children kept decoded in memory, so reopening a folder rereads nothing; 0 disables")
 	mountOptions.dataCenter = cmdMount.Flag.String("dataCenter", "", "prefer to write to the data center")
 	mountOptions.allowOthers = cmdMount.Flag.Bool("allowOthers", true, "allows other users to access the file system")
 	mountOptions.defaultPermissions = cmdMount.Flag.Bool("defaultPermissions", true, "enforce permissions by the operating system")

weed/command/mount_common.go

@@ -197,6 +197,7 @@ func buildSeaweedFileSystem(option *MountOptions, p fileSystemParams) *mount.WFS
 		CacheDirForWrite:            p.cacheDirForWrite,
 		WriteBufferSizeMB:           *option.writeBufferSizeMB,
 		CacheMetaTTlSec:             *option.cacheMetaTtlSec,
+		DirListCacheEntries:         *option.dirListCacheEntries,
 		DataCenter:                  *option.dataCenter,
 		Quota:                       int64(*option.collectionQuota) * 1024 * 1024,
 		LogicalDiskUsage:            *option.logicalDiskUsage,

weed/mount/weedfs.go

@@ -53,6 +53,7 @@ type Option struct {
 	CacheDirForWrite            string
 	WriteBufferSizeMB           int64
 	CacheMetaTTlSec             int
+	DirListCacheEntries         int
 	DataCenter                  string
 	Umask                       os.FileMode
 	Quota                       int64
@@ -303,7 +304,7 @@ func NewSeaweedFileSystem(option *Option) *WFS {
 		wfs.writeBufferAccountant.SetEvictor(wfs.evictOneWritableChunk)
 	}
 
-	wfs.metaCache = meta_cache.NewMetaCache(path.Join(option.getUniqueCacheDirForRead(), "meta"), option.UidGidMapper,
+	wfs.metaCache = meta_cache.NewMetaCacheWithListingCache(path.Join(option.getUniqueCacheDirForRead(), "meta"), option.UidGidMapper,
 		util.FullPath(option.FilerMountRootPath),
 		option.IncludeSystemEntries,
 		func(path util.FullPath) {
@@ -314,7 +315,7 @@ func NewSeaweedFileSystem(option *Option) *WFS {
 			if wfs.inodeToPath.RecordDirectoryUpdate(dirPath, time.Now(), wfs.dirHotWindow, wfs.dirHotThreshold) {
 				wfs.markDirectoryReadThrough(dirPath)
 			}
-		})
+		}, option.DirListCacheEntries)
 	wfs.metaCache.SetPinnedChildFn(wfs.isLocalOnlyEntry)
 	grace.OnInterrupt(func() {
 		// grace calls os.Exit(0) after all hooks, so WaitForAsyncFlush
@@ -506,6 +507,7 @@ func (wfs *WFS) StartBackgroundTasks() error {
 		// wipe the root's stale children through the apply loop so the delete
 		// cannot strand a concurrent rebuild cached-but-empty.
 		wfs.inodeToPath.InvalidateAllChildrenCache()
+		wfs.metaCache.InvalidateAllListings()
 		wfs.purgeDirectoryCache(util.FullPath(wfs.option.FilerMountRootPath))
 	}, follower)
 	go wfs.loopCheckQuota()