Swapoff Performance

“‘My experiments show that when there is not much free physical
memory, swapoff moves pages out of swap at a rate of approximately
5mb/sec,’ Daniel Drake noted in a recent discussion about swapoff
performance. He added, ‘I’ve read into the swap code and I have
some understanding that this is an expensive operation (and has to
be).’ Hugh Dickins acknowledged, ‘Yes, it can be shamefully slow.
But we’ve done nothing about it for years, simply because very few
actually suffer from its worst cases. You’re the first I’ve heard
complain about it in a long time: perhaps you’ll be joined by a
chorus, and we can have fun looking at it again…'”