Re: [myrinet] Re: Re: Low bandwidth

On Wed, Aug 01, 2001 at 09:49:22AM +0200, Francesco Lovergine wrote:

> > What does gm_debug say for a DMA rate?
> 
> That's interesting:
> 
> Opening board 0, port 0
> 
> DMA rate for 8192 Byte transfers (32bit / 33MHz bus)
> 1st: 8 pages from bogus sdma pg, 8 to bogus rdma
>         bus_read  (send) = 126 MBytes/s
>         bus_write (recv) = 60 MBytes/s

This is a known problem with older Alphas; here's a more modern XP1000
@ 667. By the way, I would like to collect these results for a variety
of systems; if anyone is interested in contributing, run "gm_debug"
and send me the top 30 lines, along with a description of the system
and the myrinet hardware.

DMA rate for 8192 Byte transfers (64bit / 33MHz bus)
1st: 8 pages from bogus sdma pg, 8 to bogus rdma
	bus_read  (send) = 170 MBytes/s
	bus_write (recv) = 240 MBytes/s

DMA rate for 8192 Byte transfers (64bit / 33MHz bus)
2nd: sdma a page, rdma a page 8 times
	bus_read  (send) = 170 MBytes/s
	bus_write (recv) = 240 MBytes/s

DMA rate for 8192 Byte transfers (64bit / 33MHz bus)
3rd: sdma and rdma to/from alternating pages (coarse grain)
	bus_read  (send) = 210 MBytes/s
	bus_write (recv) = 240 MBytes/s

DMA rate for 8192 Byte transfers (64bit / 33MHz bus)
4th: sdma and rdma to/from alternating pages (fine grain)
	bus_read  (send) = 221 MBytes/s
	bus_write (recv) = 240 MBytes/s