On Tue, 13 Feb 2001 12:29:16 -0800, Ion Badulescu <[EMAIL PROTECTED]> wrote:
> On Tue, 13 Feb 2001 07:06:44 -0600 (CST), Jeff Garzik
><[EMAIL PROTECTED]> wrote:
>
>> On 12 Feb 2001, Jes Sorensen wrote:
>>> In fact one has to look out for this and disable the feature in some
>>> cases. On the acenic not disabling Memory Write and Invalidate costs
>>> ~20% on performance on some systems.
>>
>> And in another message, On Mon, 12 Feb 2001, David S. Miller wrote:
>>> 3) The acenic/gbit performance anomalies have been cured
>>> by reverting the PCI mem_inval tweaks.
>>
>> Just to be clear, acenic should or should not use MWI?
With the zerocopy patch, acenic always disables MWI by default.
>> And can a general rule be applied here? Newer Tulip hardware also
>> has the ability to enable/disable MWI usage, IIRC.
>
> And so do eepro100 and starfire. On the eepro100 we're enabling MWI
> unconditionally, and on the starfire we disable it unconditionally...
>
> I should probably take a look at acenic's use of PCI_COMMAND_INVALIDATE
> to see when it gets activated. Some benchmarking would probably help,
> too -- maybe later today.
I did some testing with starfire, and the results are inconclusive --
at least on my P-III is makes absolutely no difference. Does it make
a difference on other architectures? sparc64, ia64 maybe?
I should probably rephrase this: MWI makes no difference on i386, but
it is claimed that using MWI *reduces* performance on some systems.
Are there any systems on which MWI *increases* performance?
I've added some code to the starfire driver that allows changing the
use of MWI at module load time, just in case. By default, it activates
it.
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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