.

wcfs/wcfs.go

@@ -457,18 +457,22 @@ func (bf *BigFile) Read(_ nodefs.File, dest []byte, off int64, _ fuse.Context) (
 */
 
 
-// zodbCacheControl tunes ZODB wrt caching XXX
+// zodbCacheControl implements ConnCacheControl to tune ZODB to never evict
+// ZBTree/ZBucket from live cache. We want to keep ZBTree/ZBucket always alive
+// becuse it is essentially the index where to find ZBigFile data.
+//
+// For the data itself - we put it to kernel cache and always deactivate from
+// ZODB right after that.
+//
 // XXX set it to Connection.CacheControl
 type zodbCacheControl struct {}
 
-type (cc *zodbCacheControl) WantEvict(obj Object) {
-	// we want to keep ZBTree/ZBucket always alive becuse it is essentially
-	// the index where to find ZBigFile data.
+func (cc *zodbCacheControl) WantEvict(obj Object) {
 	switch obj.(type) {
 	default:
 		return true
 
-	case *ZBtree:
+	case *ZBTree:
 	case *ZBucket:
 	}
 

wcfs/zodb.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"fmt"
 	"sync"
+	"sync/atomic"
 
 	"lab.nexedi.com/kirr/neo/go/zodb"
 
@@ -106,7 +107,7 @@ func (pyobj *pyObject) PyState() interface{}	{ return pyobj.pystate	}
 
 
 // ConnCacheControl is the interface that allows applications to influence
-// Connection decisions with respect to its cache.
+// Connection's decisions with respect to its live cache.
 type ConnCacheControl interface {
 	// WantEvict is called when object is going to be evicted from live cache and made ghost.
 	// If !ok the object will remain live.
@@ -178,6 +179,9 @@ type Connection struct {
 	objmu  sync.Mutex
 	objtab map[zodb.Oid]*WeakRef	// oid -> WeakRef(PyObject)
 	//objtab map[zodb.Oid]interface{}	// oid -> WeakRef(pyObject) | loadInProgress
+
+
+	cacheControl ConnCacheControl
 }
 
 /*
@@ -493,7 +497,7 @@ func (obj *object) pactivate(ctx context.Context) error {
 	nuse := atomic.AddInt32(&obj.refcnt, +1)
 	if nuse == 1 {
 		// we become responsible for loading object's data.
-		// XXX check .tryToKeepInRam
+		// XXX check state
 	}
 }
 
@@ -509,6 +513,12 @@ func (obj *object) pdeactivate() {
 	// no users left. Let's see whether we should transition this object to ghost.
 	// TODO state=modified -> don't drop.
 
+	if drop {
+		if cc := obj.jar.cacheControl; cc != nil {
+			drop = cc.WantEvict(obj)
+		}
+	}
+
 	if drop {
 		obj.serial  = 0
 	}