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Bug#804283: Fwd: RE: [E1000-devel] igb / ixgbe : differences between mainline and out-of-tree drivers



[Cross posting to both RFS and ITP bugs, since it's relevant to both]

Hi,

there weren't any new message on the thread I started on upstream
mailing list for a week, so I guess it's time to relay.

The complete response I received is included below, at the end of the
message.

To summarize:
- RSS, EEE, InterruptThrottleRate and QueuePair can be achieve via ethtool
- LLI parameters won't, but this is considered a rarely used feature,
not supported by recent hardware
- InterruptMode is mainly used for debug, since the driver should select
the best interrupt mode available
- VDMQ, MDD and DMAC aren't supported via ethtool and probably never will.

I personally can manage what I need with ethtool, but I'm willing to
maintain this package anyway since I already use kernel parameters
(easier to use than ethtool, although less dynamic). Also people could
find the parameters not supported by ethtool useful.

Of course I'll understand if it's not acceptable for Debian. Advice and
input welcome. I updated the version on mentor to reflect this in the
description.

Cheers,

nodens

-------- Message transféré --------
Sujet : 	RE: [E1000-devel] igb / ixgbe : differences between mainline
and out-of-tree drivers
Date : 	Tue, 10 Nov 2015 18:26:42 +0000
De : 	Tantilov, Emil S <emil.s.tantilov@intel.com>
Pour : 	Clement Hermann <nodens@nodens.org>,
e1000-devel@lists.sourceforge.net <e1000-devel@lists.sourceforge.net>



>-----Original Message-----
>From: Clement Hermann [mailto:nodens@nodens.org]
>Sent: Tuesday, November 10, 2015 3:51 AM
>To: e1000-devel@lists.sourceforge.net
>Subject: [E1000-devel] igb / ixgbe : differences between mainline and out-
>of-tree drivers
>
>Hi,
>
>I'm trying to understand the differences between the out-of-tree and the
>mainline version for igb and ixgbe drivers.
>
>The issue is, I packaged the out-of-tree version for debian, but there
>are concerns from the kernel team for allowing to maintain an
>out-of-tree driver since most features should be in the mainline driver.
>
>(see discussion on
>https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=804258 and
>https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=804283)
>
>AFAICS, the main difference is that the mainline driver doesn't support
>configuration via modules parameter.

Except for rare cases the community is against using module parameters and 
in favor of using generic tools to control the behavior of the Ethernet drivers.

>Some parameters can be controled with ethtool on mainline version:
>
> - EE: ethtool --set-eee
> - RSS: ethtool -X
>
>For some I'm unsure:
>
> - InterruptThrottleRate: ethtool -C ? Not sure if the same is achieved.
>Input welcome.
> - QueuePairs: Seems like it could be done with ethtool -L ?

That's right. 

>Other don't seen to be:
> - IntMode:Change Interrupt Mode

The driver will pick the best available interrupt mode. This parameter is
more useful for debugging than anything else. There are also ways to limit the 
support from the kernel command line, but that is usually not a good idea.

> - Node:set the starting node to allocate memory on

The driver is designed to allocate memory from the nearest NUMA node.
If I remember correctly this parameter was rejected by the community when we 
proposed it. I think this is a leftover in igb, ixgbe does not have this parameter.

> - LLIPort:Low Latency Interrupt TCP Port
> - LLIPush:Low Latency Interrupt on TCP Push flag
> - LLISize:Low Latency Interrupt on Packet Size

The LLI parameters are not generic and are no longer supported in newer HW.
There is no ethtool alternative, but we haven't seen much use of them either.

> - VMDQ:Number of Virtual Machine Device Queues
> - MDD:Malicious Driver Detection
> - DMAC: Disable or set latency for DMA Coalescing
>
>Will these functions be available via ethtool in the mainline driver
>someday ?

We always try to determine if a certain parameter can be exposed via method other
than a module parameter, but not all of the functionality has an equivalent option
in ethtool. Also some parameters are introduced as a way to test new functionality.

Thanks,
Emil





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