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

> > > 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?
Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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