Thanks to debernardis and Saturn for the good job.
I tried Swappolube for some days. I could notice an increase in fluidity, particularly when switching among several open applications.

Unfortunately I also found a use case with a clear performance degradation: streaming video files from a UPnP media server.
With Swappolube off, streaming videos from my home PC through WLAN is flawless: playback never stops for buffering. With Swappolube on, all other things being equal, playback stops for buffering every 3-10 seconds.

I made a quick test: with 'Kill allocating task' off things improve slightly but not as much as to make watching videos enjoyable (i.e., playback stops every 10-30 seconds on average). When I have some time I will try to find the best settings.