[ofa-general] [PATCH] IB/mlx4: Use pgprot_writecombine() for BlueFlame pages

[Or Gerlitz]

Roland Dreier wrote:
> The PAT work on x86 has finally made pgprot_writecombine() a usable API
> for modular drivers.  As the comment indicates, this is exactly what we
> want to use in mlx4_ib to map BlueFlame pages up to userspace, since
> using WC for these pages improves small message latency significantly.
>
> Signed-off-by: Roland Dreier <rolandd at cisco.com>
> ---
> Could someone test this patch on top of 2.6.29, and see if it provides
> the right latency benefit?  If it looks good, I'll send it upstream for 2.6.30.
Roland,

Can you elaborate a little on the expected latency benefit? If we see 
today 1us half rtt for small messages, with this patch it should go 
below? be the same for larger messages? anything else?

Or.