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

[Liu Yuan]

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.

I suggest to consider the fix if the problem is really emerging with
more information. We shouldn't fix the imaginary problem, especially
compromise the performance a lot.

Thanks,
Yuan