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SubjectRe: Frontswap [PATCH 0/4] (was Transcendent Memory): overview

> > > Nevertheless, frontswap works great today with a bare-metal
> > > hypervisor. I think it stands on its own merits, regardless
> > > of one's vision of future SSD/memory technologies.
> >
> > Even when frontswapping to RAM on a bare metal hypervisor it makes
> > sense
> > to use an async API, in case you have a DMA engine on board.
> When pages are 2MB, this may be true. When pages are 4KB and
> copied individually, it may take longer to program a DMA engine
> than to just copy 4KB.
> But in any case, frontswap works fine on all existing machines
> today. If/when most commodity CPUs have an asynchronous RAM DMA
> engine, an asynchronous API may be appropriate. Or the existing
> swap API might be appropriate. Or the synchronous frontswap API
> may work fine too. Speculating further about non-existent
> hardware that might exist in the (possibly far) future is irrelevant
> to the proposed patch, which works today on all existing x86 hardware
> and on shipping software.

If we added all the apis that worked when proposed, we'd have
unmaintanable mess by about 1996.

Why can't frontswap just use existing swap api?

(cesky, pictures)

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