Subject: Re: [PATCH 39 of 39] IB/ipath - use streaming copy in RDMA interrupt handler to reduce packet loss

From: Rick Jones <[email-masked]>
Date: Thu, 29 Jun 2006 17:44:05 -0700

David Miller wrote:
> From: Rick Jones <[email-masked]>
> Date: Thu, 29 Jun 2006 17:28:50 -0700
> 
> 
>>I thought that most PCI controllers (that is to say the things bridging 
>>PCI to the rest of the system) could do prefetching and/or that PCI-X 
>>(if not PCI, no idea about PCI-e) cards could issue multiple 
>>transactions anyway?
> 
> 
> People doing deep CMT chips have found out that all of that
> prefetching and store buffering is unnecessary when everything is so
> tightly integrated.

Then is prefetching in memcpy really that important to them (BTW besides 
  Sun/Niagra who are doing "deep CMT"?)

> All of the previous UltraSPARC boxes before Niagara had a
> streaming cache sitting on the PCI controller.  It basically
> prefetched for reads and collected writes from PCI devices
> into cacheline sized chunks.
> 
> The PCI controller in the current Niagara systems has none of that
> stuff.

Relying on PCI-X devices to issue multiple requests then?

rick jones