On Wed, 6 Mar 2002, David S. Miller wrote:
> On sparc64 you should set the burst settings to 64-byte read/write
> bursts because the PCI chipset is going to disconnect you on 64-byte
> boundaries anyways. If the chip is bursting more than this, you
> are wasting lots of PCI cycles with the retries done after the
> disconnect.
Ahh.. indeed, changing the burst size to 64 bytes (from the default 128)
makes a big difference on my ultra5, thanks for the hint. Does it make any
sense to differentiate between platforms, or is 64 a good all-around
value?
> Also make sure to use PCI READ MULTIPLE commands for DMA if the chip
> provides such an option, this helps performance on many PCI
> controllers to no end.
MRM (and MRL) seem to be enabled by default, although the chip docs are a
bit unclear about it.
Thanks,
Ion
--
It is better to keep your mouth shut and be thought a fool,
than to open it and remove all doubt.
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This archive was generated by hypermail 2b29 : Thu Mar 07 2002 - 21:01:06 EST