> > Well if you are saying that your primary objection to the > > frontswap synchronous API is that it is exposed to modules via > > some EXPORT_SYMBOLs, we can certainly fix that, at least > > unless/until there are other pseudo-RAM devices that can use it. > > > > Would that resolve your concerns? > > > > By external interfaces I mean the guest/hypervisor interface. > EXPORT_SYMBOL is an internal interface as far as I'm concerned. > > Now, the frontswap interface is also an internal interface, but it's > close to the external one. I'd feel much better if it was > asynchronous. OK, so on the one hand, you think that the proposed synchronous interface for frontswap is insufficiently extensible for other uses (presumably including KVM). On the other hand, you agree that using the existing I/O subsystem is unnecessarily heavyweight. On the third hand, Nitin has answered your questions and spent a good part of three years finding that extending the existing swap interface to efficiently support swap-to-pseudo-RAM requires some kind of in-kernel notification mechanism to which Linus has already objected. So you are instead proposing some new guest-to-host asynchronous notification mechanism that doesn't use the existing bio mechanism (and so presumably not irqs), imitates or can utilize a dma engine, and uses less cpu cycles than copying pages. AND, for long-term maintainability, you'd like to avoid creating a new guest-host API that does all this, even one that is as simple and lightweight as the proposed frontswap hooks. Does that summarize your objection well? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href