X move to zodb/storage.Cache & xcontainer/list

go/neo/client/list.go → go/xcommon/xcontainer/list/list.go

@@ -17,27 +17,30 @@
 // See COPYING file for full licensing terms.
 // See https://www.nexedi.com/licensing for rationale and options.
 
-package client
-// base for intrusive list
+// Package list provides intrusive double-linked lists.
+package list
 
-// listHead is a list head entry for an element in an intrusive doubly-linked list.
+// Head is a list head entry for an element in an intrusive doubly-linked list.
 //
 // XXX doc how to get to container of this list head via unsafe.OffsetOf
 //
 // always call Init() to initialize a head before using it.
-type listHead struct {
+type Head struct {
 	// XXX needs to be created with .next = .prev = self
-	next, prev *listHead
+	next, prev *Head
 }
 
+func (h *Head) Next() *Head { return h.next }
+func (h *Head) Prev() *Head { return h.prev }
+
 // Init initializes a head making it point to itself via .next and .prev
-func (h *listHead) Init() {
+func (h *Head) Init() {
 	h.next = h
 	h.prev = h
 }
 
 // Delete deletes h from its list
-func (h *listHead) Delete() {
+func (h *Head) Delete() {
 	h.next.prev = h.prev
 	h.prev.next = h.next
 	h.Init()
@@ -45,7 +48,7 @@ func (h *listHead) Delete() {
 
 // MoveBefore moves a to be before b
 // XXX ok to move if a was not previously on the list?
-func (a *listHead) MoveBefore(b *listHead) {
+func (a *Head) MoveBefore(b *Head) {
 	a.Delete()
 
 	a.next = b

go/neo/client/cache.go → go/zodb/storage/cache.go

@@ -17,7 +17,7 @@
 // See COPYING file for full licensing terms.
 // See https://www.nexedi.com/licensing for rationale and options.
 
-package client
+package storage
 // cache management
 
 // XXX gotrace ... -> gotrace gen ...
@@ -29,19 +29,16 @@ import (
 	"sync"
 	"unsafe"
 
-//	"github.com/kylelemons/godebug/pretty"
 	"lab.nexedi.com/kirr/neo/go/zodb"
+
+	"lab.nexedi.com/kirr/neo/go/xcommon/xcontainer/list"
 )
 
-// storLoader represents loading part of a storage
-// XXX -> zodb?
-type storLoader interface {
-	Load(xid zodb.Xid) (data []byte, serial zodb.Tid, err error)
-}
+// TODO maintain nhit / nmiss + way to read cache stats
 
-// Cache adds RAM caching layer over a storage
+// Cache adds RAM caching layer over a storage.
 type Cache struct {
-	loader storLoader
+	loader StorLoader
 
 	mu sync.RWMutex
 
@@ -55,7 +52,7 @@ type Cache struct {
 	gcCh chan struct{} // signals gc to run
 
 	gcMu sync.Mutex
-	lru  listHead	// revCacheEntries in LRU order
+	lru  lruHead	// revCacheEntries in LRU order
 	size int	// cached data size in bytes
 
 	sizeMax int	// cache is allowed to occupy not more than this
@@ -80,7 +77,7 @@ type oidCacheEntry struct {
 // revCacheEntry is information about 1 cached oid revision
 type revCacheEntry struct {
 	parent *oidCacheEntry	// oidCacheEntry holding us
-	inLRU  listHead		// in Cache.lru; protected by Cache.gcMu
+	inLRU  lruHead		// in Cache.lru; protected by Cache.gcMu
 
 	// we know that loadBefore(oid, .before) will give this .serial:oid.
 	//
@@ -107,16 +104,20 @@ type revCacheEntry struct {
 	accounted bool		// whether rce size accounted in cache size; protected by .parent's lock
 }
 
+// StorLoader represents loading part of a storage.
+// XXX -> zodb?
+type StorLoader interface {
+	Load(xid zodb.Xid) (data []byte, serial zodb.Tid, err error)
+}
+
 // lock order: Cache.mu   > oidCacheEntry
 //             Cache.gcMu > oidCacheEntry
 
-// XXX maintain nhit / nmiss?
-
 
 // NewCache creates new cache backed up by loader.
 //
 // The cache will use not more than ~ sizeMax bytes of RAM for cached data.
-func NewCache(loader storLoader, sizeMax int) *Cache {
+func NewCache(loader StorLoader, sizeMax int) *Cache {
 	c := &Cache{
 		loader:   loader,
 		entryMap: make(map[zodb.Oid]*oidCacheEntry),
@@ -146,7 +147,7 @@ func (c *Cache) SetSizeMax(sizeMax int) {
 
 // Load loads data from database via cache.
 //
-// If data is already in cache cached content is returned.
+// If data is already in cache - cached content is returned.
 func (c *Cache) Load(xid zodb.Xid) (data []byte, serial zodb.Tid, err error) {
 	rce, rceNew := c.lookupRCE(xid)
 
@@ -154,7 +155,7 @@ func (c *Cache) Load(xid zodb.Xid) (data []byte, serial zodb.Tid, err error) {
 	if !rceNew {
 		<-rce.ready
 		c.gcMu.Lock()
-		rce.inLRU.MoveBefore(&c.lru)
+		rce.inLRU.MoveBefore(&c.lru.Head)
 		c.gcMu.Unlock()
 
 	// rce is not in cache - this goroutine becomes responsible for loading it
@@ -366,23 +367,19 @@ func (c *Cache) loadRCE(rce *revCacheEntry, oid zodb.Oid) {
 	// update lru & cache size
 	gcrun := false
 	c.gcMu.Lock()
-	//xv1 := map[string]interface{}{"lru": &c.lru, "rce": &rce.inLRU}
-	//fmt.Printf("aaa:\n%s\n", pretty.Sprint(xv1))
+
 	if rcePrevDropped != nil {
 		rcePrevDropped.inLRU.Delete()
 	}
 	if !rceDropped {
-		rce.inLRU.MoveBefore(&c.lru)
+		rce.inLRU.MoveBefore(&c.lru.Head)
 	}
-	//xv2 := map[string]interface{}{"lru": &c.lru, "rce": &rce.inLRU}
-	//fmt.Printf("\n--------\n%s\n\n\n", pretty.Sprint(xv2))
-
 	c.size += δsize
 	if c.size > c.sizeMax {
 		gcrun = true
 	}
-	c.gcMu.Unlock()
 
+	c.gcMu.Unlock()
 	if gcrun {
 		c.gcsignal()
 	}
@@ -495,7 +492,7 @@ func (c *Cache) gc() {
 		}
 
 		// kill 1 least-used rce
-		h := c.lru.next
+		h := c.lru.Next()
 		if h == &c.lru {
 			panic("cache: gc: empty .lru but .size > .sizeMax")
 		}
@@ -608,8 +605,17 @@ func (rce *revCacheEntry) userErr(xid zodb.Xid) error {
 	return rce.err
 }
 
+// list head that knows it is in revCacheEntry.inLRU
+type lruHead struct {
+	list.Head
+}
+
+// XXX vvv strictly speaking -unsafe.Offsetof(h.Head)
+func (h *lruHead) Next() *lruHead { return (*lruHead)(unsafe.Pointer(h.Head.Next())) }
+func (h *lruHead) Prev() *lruHead { return (*lruHead)(unsafe.Pointer(h.Head.Prev())) }
+
 // revCacheEntry: .inLRU -> .
-func (h *listHead) rceFromInLRU() (rce *revCacheEntry) {
+func (h *lruHead) rceFromInLRU() (rce *revCacheEntry) {
 	urce := unsafe.Pointer(uintptr(unsafe.Pointer(h)) - unsafe.Offsetof(rce.inLRU))
 	return (*revCacheEntry)(urce)
 }

go/neo/client/cache_test.go → go/zodb/storage/cache_test.go

@@ -17,7 +17,7 @@
 // See COPYING file for full licensing terms.
 // See https://www.nexedi.com/licensing for rationale and options.
 
-package client
+package storage
 
 import (
 	"bytes"
@@ -199,10 +199,10 @@ func TestCache(t *testing.T) {
 		t.Helper()
 		size := 0
 		var mruv []*revCacheEntry
-		for hp, h := &c.lru, c.lru.prev; h != &c.lru; hp, h = h, h.prev {
+		for hp, h := &c.lru, c.lru.Prev(); h != &c.lru; hp, h = h, h.Prev() {
 			//xv := []interface{}{&c.lru, h.rceFromInLRU()}
 			//debug.Print(xv)	// &c.lru, h.rceFromInLRU())
-			if h.next != hp {
+			if h.Next() != hp {
 				t.Fatalf("LRU list .next/.prev broken for\nh:\n%s\n\nhp:\n%s\n",
 					debug.Sprint(h), debug.Sprint(hp))
 			}

go/zodb/storage/doc.go

+// Copyright (C) 2017  Nexedi SA and Contributors.
+//                     Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
+
+// Package storage provides common bits related to ZODB storages.	XXX text
+package storage

go/neo/client/ztrace.go → go/zodb/storage/ztrace.go

 // Code generated by lab.nexedi.com/kirr/go123/tracing/cmd/gotrace; DO NOT EDIT.
 
-package client
+package storage
 // code generated for tracepoints
 
 import (
@@ -63,4 +63,4 @@ func traceCacheGCStart_Attach(pg *tracing.ProbeGroup, probe func(c *Cache)) *tra
 }
 
 // trace export signature
-func _trace_exporthash_624de1c8d179b91f695f79fec7f7cdb7386501f4() {}
+func _trace_exporthash_46a80e8af5056736069c296a95ad4c94388ab850() {}