[parisc-linux] C3000 and 2.6 - need config help

[M. Grabert]

On Wed, 26 Nov 2003, Grant Grundler wrote:

> However, I just now wonder if the limiting factor is not the IDE if the
> kernel is copying data to/from kernel to user space.  Our copy_to/from_user
> could be alot more efficient (2x guesstimate) for the PA8500 CPU.
> I see max bandwidth of 4-5MB/s on a PA8600 (552Mhz) over 100BT.

The limiting factor is definitely not the IDE hard disk, it's a new
Seagate 120GB which has a sustained data transfer rate of >30MB/s.

The max. transfer rate of any 100BT network is around 5MByte/s.

Personally I also get something between 4-5MB/s from any host to any
hosy in my home network. If I do a network transfer to the C3k (IDE hard disk),
I get about 4.5MB/s, but after a while the transfer stalls for a short
time, and then continues. However I see sustained 4.5MB/s to my C3k if I
write to any of the SCSI hard disks - without any stalls.

I suppose if it tries to write the data to the IDE hard disk (3.3MB/s),
it can't keep up with the speed of the network (4.5MB/s), so it buffers
the data in the RAM. At some point the buffer is full and the kernel
delays the networks transfer until the buffer content is written to the
IDE disk.


> With a 32X CD-ROM drive in my c3k, "time dd" is only getting 925 KB/s.
> I'll guess a few more factors could be muddying the waters here.

That's equivalent to a 5-6X CD-ROM. Ouch.

[...]

Quite a lot old IDE cdroms drives don't support dma transfers.
Hower you'll get the same message if you try to enable DMA if you have a
kernel that doesn't have a driver with DMA support for your IDE chipset.

I honestly don't thing DMA works ...


 Max