[sheepdog] [PATCH 2/2] farm: drop fcntl lock

[MORITA Kazutaka]

At Tue, 05 Jun 2012 22:55:21 +0800,
Liu Yuan wrote:
> 
> On 06/05/2012 10:38 PM, MORITA Kazutaka wrote:
> 
> > The below change to the qemu block driver would fix the problem.
> > I think this kind of ordering should be done in the gateway node,
> > though.
> 
> 
> This will dramatically hurt the IO performance, at least for object
> cache, I can see concurrent access to the same object, but NOT
> overlapped at all.
> 
> Most of disk driver default to 512K for maximum IO size, this means most
> of chances we will get requests(split by OS driver and block layer) to
> access the same 4M object.

Concurrent accesses to the "same object" is not what I wanted to say.
We can change the overlap check from "same object" to "same sector"
easily.  I'm just suggesting an approach to order requests in the
client side.

Thanks,

Kazutaka