[Xen-devel] Re: Tmem [PATCH 0/5] (Take 3): Transcendent memory

[Pavel Machek <pavel@xxxxxx>]

Hi!

> > achive this using
> > > > some existing infrastructure in kernel.
> > > 
> > > Hi Nitin --
> > > 
> > > Sorry if I sounded overly negative... too busy around the holidays.
> > > 
> > > I'm definitely OK with exploring alternatives.  I just think that
> > > existing kernel mechanisms are very firmly rooted in the notion
> > > that either the kernel owns the memory/cache or an asynchronous
> > > device owns it.  Tmem falls somewhere in between and is very
> > 
> > Well... compcache seems to be very similar to preswap: in preswap case
> > you don't know if hypervisor will have space, in ramzswap you don't
> > know if data are compressible.
> 
> Hi Pavel --
> 
> Yes there are definitely similarities too.  In fact, I started
> prototyping preswap (now called frontswap) with Nitin's
> compcache code.  IIRC I ran into some problems with compcache's
> difficulties in dealing with failed "puts" due to dynamic
> changes in size of hypervisor-available-memory.
> 
> Nitin may have addressed this in later versions of ramzswap.

That would be cool to find out.

> One feature of frontswap which is different than ramzswap is
> that frontswap acts as a "fronting store" for all configured
> swap devices, including SAN/NAS swap devices.  It doesn't
> need to be separately configured as a "highest priority" swap
> device.  In many installations and depending on how ramzswap

Ok, I'd call it a bug, not a feature :-).
                                                                Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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