[Sheepdog] [PATCH v5 4/8] sheep: teach sheep to use object cache

[Liu Yuan]

On 03/26/2012 05:26 PM, huxinwei wrote:

> My point is about _different_ VMs reading the same object.
> It doesn't matter how you optimize guest here ...


We can't read the same object from mutiple VMs right now. (Farm
originally supports naming the object by hash content for data
deduplication)

If we do, yes, in this scenario, we would benefit some workloads (mostly
read, seldom write) from a unified and content-named cache.

But for a general cache, if we have a unified cache (be it in memory or
on disk) that serve a lot of VM requests concurrently, I think we would
meet the lock contention problem, hardly to be scalable.

So we might later have a unified cache complementarity(a transparent
write through cache) in memory for this kind of read acceleration on top
of object cache, which just aims to be generally reducing the network
traffic by absorbing IO requests locally.

Thanks,
Yuan