Messages in this thread | | | Date | Sun, 12 Jul 2009 13:39:07 -0700 (PDT) | From | Dan Magenheimer <> | Subject | RE: [Xen-devel] Re: [RFC PATCH 0/4] (Take 2): transcendent memory ("tmem") for Linux |
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> CMM2 and tmem are not any different in this regard; both require OS > modification, and both make information available to the > hypervisor. In > fact CMM2 is much more intrusive (but on the other hand provides much > more information). > > > For those that believe it will be pervasive in the > > future, finding the right balance is a critical step > > in operating system evolution. > > You're arguing for CMM2 here IMO.
I'm arguing that both are a good thing and a step in the right direction. In some ways, tmem is a bigger step and in some ways CMM2 is a bigger step.
> My take on this is that precache (predecache?) / preswap can be > implemented even without tmem by using write-through backing for the > virtual disk. For swap this is actually slight;y more efficient than > tmem preswap, for preuncache slightly less efficient (since > there will > be some double caching). So I'm more interested in other use > cases of tmem/CMM2. > > Right, the transient uses of tmem when applied to disk objects > (swap/pagecache) are very similar to disk caches. Which is > why you can > get a very similar effect when caching your virtual disks; > this can be > done without any guest modification.
Write-through backing and virtual disk cacheing offer a similar effect, but it is far from the same.
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