Look my example:
np.random.seed(42)
data = (ImageDataBunch.from_folder(path=path, train=path_images,valid_pct=0.2)
.use_partial_data(0.1)
.split_by_rand_pct()
.label_from_folder()
.transform(tfms,size=128)
.databunch(bs=64)
.normalize(imagenet_stats))
I use .use_partial_data(0.1) to use only 10% of my datasets:
See also:
https://docs.fast.ai/data_block.html#ItemList.use_partial_data