Messages in this thread |  | | | Date | Wed, 24 Jun 2009 17:04:21 +0200 | | From | Pavel Machek <> | | Subject | Re: [RFC] transcendent memory for Linux |
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Hi!
This description (whole mail) needs to go into Documentation/, somewhere.
> Normal memory is directly addressable by the kernel, > of a known normally-fixed size, synchronously accessible, > and persistent (though not across a reboot). ... > Transcendent memory, or "tmem" for short, provides a > well-defined API to access this unusual class of memory. > The basic operations are page-copy-based and use a flexible > object-oriented addressing mechanism. Tmem assumes
Should this API be documented, somewhere? Is it in-kernel API or does userland see it?
> "Preswap" IS persistent, but for various reasons may not always > be available for use, again due to factors that may not be > visible to the kernel (but, briefly, if the kernel is being > "good" and has shared its resources nicely, then it will be > able to use preswap, else it will not). Once a page is put, > a get on the page will always succeed. So when the kernel > finds itself in a situation where it needs to swap out a page, > it first attempts to use preswap. If the put works, a disk > write and (usually) a disk read are avoided. If it doesn't, > the page is written to swap as usual. Unlike precache, whether
Ok, how much slower this gets in the worst case? Single hypercall to find out that preswap is unavailable? I guess that compared to disk access that's lost in the noise? Pavel
-- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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