HOG setSVMDetector slow

I'm using HOG with custom svm. I've used https://github.com/opencv/opencv/blob/master/samples/cpp/train_HOG.cpp but my feature vector has 2268 features and get_svm_detector() give me 2269 support vectors, this don't give me error but hog.detectMultiScale is very slow ( ~ 6 s), why? With svmLight I get 2268 support vectors and hog.detectMultiScale takes about ~64 ms.