kvcache: Pass granular cache size into implementations

Currently the runner computes the kv size needed and creates a
cache of that size. This is the context size times number of
parallel sequences.

Cache implementations can make better decisions about their memory
usage, so instead pass in the required capacity, number of sequences
and maximum batch size. For now, the causal cache just uses this to
compute the size in the same way as before.

kvcache/cache.go

@@ -43,8 +43,13 @@ type Cache interface {
 
 	// ** cache management **
 
-	// Init sets up runtime parameters
-	Init(backend ml.Backend, dtype ml.DType, capacity int32)
+	// Init sets up runtime parameters.
+	// backend: Used to allocate cache data storage and execute management operations (such as defrag)
+	// dtype: The data type for storing cache entries
+	// maxSequences: The maximum number of sequences stored in the cache - across all batches
+	// capacity: The number of cache entries to store, per sequence
+	// maxBatch: The maximum number of tokens that can occur in a single batch
+	Init(backend ml.Backend, dtype ml.DType, maxSequences, capacity, maxBatch int)
 
 	// Close closes the cache and frees resources associated with it
 	Close()

kvcache/causal.go

@@ -20,7 +20,6 @@ type shiftFn func(ctx ml.Context, layer int, key, shift ml.Tensor) (ml.Tensor, e
 // The mask is of shape history size, batch size
 type Causal struct {
 	DType      ml.DType
-	Capacity   int32
 	windowSize int32
 
 	opts CausalOptions
@@ -98,7 +97,7 @@ func NewSWACache(windowSize int32, shift shiftFn) *Causal {
 	}
 }
 
-func (c *Causal) Init(backend ml.Backend, dtype ml.DType, capacity int32) {
+func (c *Causal) Init(backend ml.Backend, dtype ml.DType, maxSequences, capacity, maxBatch int) {
 	if c.config == nil {
 		var config ml.CacheConfig
 		if cc, ok := backend.(ml.BackendCacheConfig); ok {
@@ -119,9 +118,11 @@ func (c *Causal) Init(backend ml.Backend, dtype ml.DType, capacity int32) {
 		c.config.MaskDType = ml.DTypeF32
 	}
 
+	cacheSize := maxSequences * capacity
+	cacheSize = roundUp(cacheSize, c.config.CachePadding)
+	c.cells = make([]cacheCell, cacheSize)
+
 	c.DType = dtype
-	c.Capacity = int32(roundUp(int(capacity), c.config.CachePadding))
-	c.cells = make([]cacheCell, c.Capacity)
 	c.cellRanges = make(map[int]cellRange)
 	c.backend = backend
 }
@@ -210,7 +211,7 @@ func (c *Causal) findStartLoc() (int, error) {
 		}
 	}
 
-	return 0, fmt.Errorf("%w (length: %v)", ErrKvCacheFull, c.Capacity)
+	return 0, fmt.Errorf("%w (length: %v)", ErrKvCacheFull, len(c.cells))
 }
 
 func roundDown(length, pad int) int {
@@ -265,7 +266,7 @@ func (c *Causal) buildMask(ctx ml.Context) (ml.Tensor, error) {
 	return maskTensor, nil
 }
 
-func (c *Causal) moveCells(ctx ml.Context, src, dst, len int) {
+func (c *Causal) moveCells(ctx ml.Context, src, dst, length int) {
 	for i, key := range c.keys {
 		if key == nil {
 			continue
@@ -275,8 +276,8 @@ func (c *Causal) moveCells(ctx ml.Context, src, dst, len int) {
 		numKVHeads := key.Dim(1)
 		rowSize := key.Stride(2)
 
-		kSrcView := key.View(ctx, rowSize*src, kHeadDim*numKVHeads*len)
-		kDstView := key.View(ctx, rowSize*dst, kHeadDim*numKVHeads*len)
+		kSrcView := key.View(ctx, rowSize*src, kHeadDim*numKVHeads*length)
+		kDstView := key.View(ctx, rowSize*dst, kHeadDim*numKVHeads*length)
 
 		value := c.values[i]
 		var vSrcView, vDstView ml.Tensor
@@ -284,14 +285,14 @@ func (c *Causal) moveCells(ctx ml.Context, src, dst, len int) {
 			vHeadDim := value.Dim(1)
 			elemSize := value.Stride(0)
 
-			vSrcView = value.View(ctx, elemSize*src, len, int(c.Capacity)*elemSize, vHeadDim*numKVHeads)
-			vDstView = value.View(ctx, elemSize*dst, len, int(c.Capacity)*elemSize, vHeadDim*numKVHeads)
+			vSrcView = value.View(ctx, elemSize*src, length, len(c.cells)*elemSize, vHeadDim*numKVHeads)
+			vDstView = value.View(ctx, elemSize*dst, length, len(c.cells)*elemSize, vHeadDim*numKVHeads)
 		} else {
 			vHeadDim := value.Dim(0)
 			rowSize := value.Stride(2)
 
-			vSrcView = value.View(ctx, rowSize*src, vHeadDim*numKVHeads*len)
-			vDstView = value.View(ctx, rowSize*dst, vHeadDim*numKVHeads*len)
+			vSrcView = value.View(ctx, rowSize*src, vHeadDim*numKVHeads*length)
+			vDstView = value.View(ctx, rowSize*dst, vHeadDim*numKVHeads*length)
 		}
 
 		ctx.Forward(
@@ -480,14 +481,14 @@ func (c *Causal) Put(ctx ml.Context, key, value ml.Tensor) {
 	}
 
 	if _, ok := c.keys[c.curLayer]; !ok {
-		c.keys[c.curLayer] = c.ctxs[c.curLayer].Zeros(c.DType, kHeadDim, numKVHeads, int(c.Capacity))
+		c.keys[c.curLayer] = c.ctxs[c.curLayer].Zeros(c.DType, kHeadDim, numKVHeads, len(c.cells))
 	}
 
 	if _, ok := c.values[c.curLayer]; !ok {
 		if c.config.PermutedV {
-			c.values[c.curLayer] = c.ctxs[c.curLayer].Zeros(c.DType, int(c.Capacity), vHeadDim, numKVHeads)
+			c.values[c.curLayer] = c.ctxs[c.curLayer].Zeros(c.DType, len(c.cells), vHeadDim, numKVHeads)
 		} else {
-			c.values[c.curLayer] = c.ctxs[c.curLayer].Zeros(c.DType, vHeadDim, numKVHeads, int(c.Capacity))
+			c.values[c.curLayer] = c.ctxs[c.curLayer].Zeros(c.DType, vHeadDim, numKVHeads, len(c.cells))
 		}
 	}
 
@@ -498,7 +499,7 @@ func (c *Causal) Put(ctx ml.Context, key, value ml.Tensor) {
 		elemSize := c.values[c.curLayer].Stride(0)
 
 		value = value.Permute(ctx, 1, 2, 0, 3)
-		ctx.Forward(value.Copy(ctx, c.values[c.curLayer].View(ctx, elemSize*c.curLoc, batchSize, int(c.Capacity)*elemSize, vHeadDim*numKVHeads)))
+		ctx.Forward(value.Copy(ctx, c.values[c.curLayer].View(ctx, elemSize*c.curLoc, batchSize, len(c.cells)*elemSize, vHeadDim*numKVHeads)))
 	} else {
 		rowSize := c.values[c.curLayer].Stride(2)
 

kvcache/causal_test.go

@@ -25,7 +25,7 @@ func TestStore(t *testing.T) {
 	cache := NewCausalCache(nil)
 	defer cache.Close()
 
-	cache.Init(backend, ml.DTypeF16, 16)
+	cache.Init(backend, ml.DTypeF16, 1, 16, 16)
 
 	tests := []testCase{
 		{
@@ -58,7 +58,7 @@ func TestSWA(t *testing.T) {
 	cache := NewSWACache(1, nil)
 	defer cache.Close()
 
-	cache.Init(backend, ml.DTypeF32, 16)
+	cache.Init(backend, ml.DTypeF32, 1, 16, 16)
 
 	tests := []testCase{
 		{
@@ -81,7 +81,7 @@ func TestSequences(t *testing.T) {
 	cache := NewCausalCache(nil)
 	defer cache.Close()
 
-	cache.Init(backend, ml.DTypeF16, 16)
+	cache.Init(backend, ml.DTypeF16, 1, 16, 16)
 
 	tests := []testCase{
 		{
@@ -116,7 +116,7 @@ func TestRemove(t *testing.T) {
 	})
 	defer cache.Close()
 
-	cache.Init(backend, ml.DTypeF16, 16)
+	cache.Init(backend, ml.DTypeF16, 1, 16, 16)
 
 	tests := []testCase{
 		{
@@ -181,7 +181,7 @@ func TestDefrag(t *testing.T) {
 	})
 	defer cache.Close()
 
-	cache.Init(backend, ml.DTypeF16, 16)
+	cache.Init(backend, ml.DTypeF16, 1, 16, 16)
 
 	tests := []testCase{
 		{
@@ -229,7 +229,7 @@ func TestCopy(t *testing.T) {
 	cache := NewCausalCache(func(ctx ml.Context, layer int, key, shift ml.Tensor) (ml.Tensor, error) { return key, nil })
 	defer cache.Close()
 
-	cache.Init(backend, ml.DTypeF16, 16)
+	cache.Init(backend, ml.DTypeF16, 1, 16, 16)
 
 	tests := []testCase{
 		{

kvcache/encoder.go

@@ -49,7 +49,7 @@ func NewEncoderCache() *EncoderCache {
 	}
 }
 
-func (c *EncoderCache) Init(backend ml.Backend, dtype ml.DType, capacity int32) {
+func (c *EncoderCache) Init(backend ml.Backend, dtype ml.DType, maxSequences, capacity, maxBatch int) {
 	if c.config == nil {
 		var config ml.CacheConfig
 		if cc, ok := backend.(ml.BackendCacheConfig); ok {
@@ -58,6 +58,10 @@ func (c *EncoderCache) Init(backend ml.Backend, dtype ml.DType, capacity int32)
 		c.config = &config
 	}
 
+	if maxSequences > 1 {
+		panic(fmt.Errorf("encoder cache does not support multiple sequences; requested: %v", maxSequences))
+	}
+
 	if c.config.CachePadding != 0 && c.config.CachePadding != 1 {
 		panic(fmt.Errorf("encoder cache is unable to enforce requested CachePadding (%v)", c.config.CachePadding))
 	}

kvcache/wrapper.go

@@ -23,9 +23,9 @@ func NewWrapperCache(caches ...Cache) *WrapperCache {
 	}
 }
 
-func (c *WrapperCache) Init(backend ml.Backend, dtype ml.DType, capacity int32) {
+func (c *WrapperCache) Init(backend ml.Backend, dtype ml.DType, maxSequences, capacity, maxBatch int) {
 	for _, cache := range c.caches {
-		cache.Init(backend, dtype, capacity)
+		cache.Init(backend, dtype, maxSequences, capacity, maxBatch)
 	}
 }
 

runner/ollamarunner/cache.go

@@ -31,8 +31,10 @@ type InputCache struct {
 	cache kvcache.Cache
 }
 
-func NewInputCache(model model.Model, kvCacheType string, kvSize int32, numSlots int, multiUserCache bool) (*InputCache, error) {
-	if kvSize/int32(numSlots) < 1 {
+func NewInputCache(model model.Model, kvCacheType string, kvSize int32, numSlots int, batchSize int, multiUserCache bool) (*InputCache, error) {
+	numCtx := kvSize / int32(numSlots)
+
+	if numCtx < 1 {
 		return nil, fmt.Errorf("must have at least one kv cache entry per parallel sequence (kv: %v parallel: %v)", kvSize, numSlots)
 	}
 
@@ -44,11 +46,11 @@ func NewInputCache(model model.Model, kvCacheType string, kvSize int32, numSlots
 
 	cache := model.Config().Cache
 	if cache != nil {
-		cache.Init(model.Backend(), kvCacheTypeFromStr(kvCacheType), kvSize)
+		cache.Init(model.Backend(), kvCacheTypeFromStr(kvCacheType), numSlots, int(numCtx), batchSize)
 	}
 
 	return &InputCache{
-		numCtx:         kvSize / int32(numSlots),
+		numCtx:         numCtx,
 		enabled:        cache != nil,
 		slots:          slots,
 		multiUserCache: multiUserCache,

runner/ollamarunner/runner.go

@@ -699,7 +699,7 @@ func (s *Server) loadModel(
 		panic("loras are not yet implemented")
 	}
 
-	s.cache, err = NewInputCache(s.model, kvCacheType, int32(kvSize), parallel, multiUserCache)
+	s.cache, err = NewInputCache(s.model, kvCacheType, int32(kvSize), parallel, s.batchSize, multiUserCache)
 	if err != nil {
 		panic(err)
 	}