netdev - Re: [PATCH 2/5] e1000e: Add interrupt moderation run-time ethtool interface

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Date:	Mon, 14 Apr 2008 21:53:30 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jeff Garzik <jeff@...zik.org>
CC:	Auke Kok <auke-jan.h.kok@...el.com>, netdev@...r.kernel.org,
	e1000-devel@...ts.sourceforge.net
Subject: Re: [PATCH 2/5] e1000e: Add interrupt moderation run-time ethtool
 interface

Jeff Garzik wrote:
> Andi Kleen wrote:
>> Auke Kok <auke-jan.h.kok@...el.com> writes:
>>
>>> The ethtool -c / -C interface can now be used to modify the
>>> irq moderation algorithm. This change does not require an
>>> adapter reset and can thus be used at all times. The adapter
>>> only supports changing/reading rx-usecs which has special
>>> values for 0, 1 and 3:
>>>
>>> 0 - no irq moderation whatsoever
>>> 1 - normal moderation favoring regular mixed traffic (default)
>>> 3 - best attempt at low latency possible at cost of CPU
>>
>> It would be nice if ethtool instead of having this as a obscure magic
>> number had a higher level "--low-latency" or similar parameter
>> (that could also potentially set similar settings on other NICs)
> 
> That would be fine with me -- that's one of the goals of ethtool:  make
> the setting of hardware-specific settings as generic and easy as possible.

I think this would require new ethtool interfaces (NIC_POLICY ?) so that
the driver can decide what the right settings are.

Otherwise you would need to hard code a conversion table into the user
program, which is probably a bad idea.

-Andi

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