yeah

overlay/virtqueue/split_virtqueue.go

@@ -47,6 +47,7 @@ type SplitQueue struct {
 	// offerMutex is used to synchronize calls to
 	// [SplitQueue.OfferDescriptorChain].
 	offerMutex sync.Mutex
+	pageSize   int
 }
 
 // NewSplitQueue allocates a new [SplitQueue] in memory. The given queue size
@@ -58,7 +59,8 @@ func NewSplitQueue(queueSize int) (_ *SplitQueue, err error) {
 	}
 
 	sq := SplitQueue{
-		size: queueSize,
+		size:     queueSize,
+		pageSize: os.Getpagesize(),
 	}
 
 	// Clean up a partially initialized queue when something fails.
@@ -267,9 +269,10 @@ func (sq *SplitQueue) consumeUsedRing(ctx context.Context) error {
 func (sq *SplitQueue) OfferDescriptorChain(outBuffers [][]byte, numInBuffers int, waitFree bool) (uint16, error) {
 	sq.ensureInitialized()
 
+	// TODO change this
 	// Each descriptor can only hold a whole memory page, so split large out
 	// buffers into multiple smaller ones.
-	outBuffers = splitBuffers(outBuffers, os.Getpagesize())
+	outBuffers = splitBuffers(outBuffers, sq.pageSize)
 
 	// Synchronize the offering of descriptor chains. While the descriptor table
 	// and available ring are synchronized on their own as well, this does not
@@ -411,7 +414,17 @@ func align(index, alignment int) int {
 
 // splitBuffers processes a list of buffers and splits each buffer that is
 // larger than the size limit into multiple smaller buffers.
+// If none of the buffers are too big though, do nothing, to avoid allocation for now
 func splitBuffers(buffers [][]byte, sizeLimit int) [][]byte {
+	for i := range buffers {
+		if len(buffers[i]) > sizeLimit {
+			return reallySplitBuffers(buffers, sizeLimit)
+		}
+	}
+	return buffers
+}
+
+func reallySplitBuffers(buffers [][]byte, sizeLimit int) [][]byte {
 	result := make([][]byte, 0, len(buffers))
 	for _, buffer := range buffers {
 		for added := 0; added < len(buffer); added += sizeLimit {