Re: TCP RDMA option to accelerate NFS, CIFS, SCSI, etc.

[Zachary Amsden <zamsden@cthulhu.engr.sgi.com>]

>    Date: Thu, 24 Feb 2000 17:09:51 -0700
>    From: "Justin T. Gibbs" <gibbs@freebsd.org>
> 
>    In the case of a server response, RDMA benefits the client, not the
>    server, so I fail to see why your example is problematic.  Zero
>    copy send is not what this standard addresses.
> 
> With client memory bus bandwidth in the multi-gigabyte per second
> range, who needs to avoid the single copy?  How much NFS and web
> surfing does one need to do before this is would really come into
> play?

With network bandwidth approaching memory bus bandwidth, it becomes an issue.  
A single copy receive uses 3x the bus bandwidth of a zero copy implementation 
(or worse if not aligned properly), and also poisons many more cachelines.

-- 
Zachary Amsden  zamsden@engr.sgi.com  (650) 933-6919  09U-510  Core Protocols