As far as I know, we can quantize weight in per-channel mode by using default_per_channel_weight_observer. But I did not see any per_channel related configuration for activation.
Is possible to do it for activation?
Sorry for the late reply. You should be able to set this by changing the qconfig. See here for more details.
I think you should be able to use default_per_channel_weight_observer, from the implementation here it looks like it’s just calling PerChannelObserver with dtype=int8.