netdev - Re: [net-next 11/13] igb: Make Tx budget for NAPI user adjustable

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Message-ID: <1316475390.2184.8.camel@jtkirshe-mobl>
Date:	Mon, 19 Sep 2011 16:36:29 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	"Duyck, Alexander H" <alexander.h.duyck@...el.com>
Cc:	David Miller <davem@...emloft.net>,
	"bhutchings@...arflare.com" <bhutchings@...arflare.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>
Subject: Re: [net-next 11/13] igb: Make Tx budget for NAPI user adjustable

On Mon, 2011-09-19 at 15:27 -0700, Duyck, Alexander H wrote:
> On 09/19/2011 02:00 PM, David Miller wrote:
> > From: Alexander Duyck<alexander.h.duyck@...el.com>
> > Date: Mon, 19 Sep 2011 09:32:18 -0700
> >> The fact is ixgbe has been using this parameter this way for over 2
> >> years now and the main goal of this patch was just to synchronize how
> >> things work on igb and ixgbe.
> >>
> >> Our hardware doesn't have a mechanism for firing an interrupt after X
> >> number of frames so instead we simply have modified things so that we
> >> will only process X number of frames and then fire another
> >> interrupt/poll if needed.  As such we aren't that far out of
> >> compliance with the meaning of how this parameter is supposed to be
> >> used.
> > All I can say is this was a huge mistake you therefore need to revert
> > the IXGBE change, these ethtool settings are not for changing NAPI or
> > software interrupt behavior.
> >
> > And if you guys plan to be difficult on this and refuse to remove the
> > IXGBE bits, I'm letting you guys know ahead of time that I'll do it
> > for you.
> >
> > If the hardware can't support this facility, neither should these
> > ethtool hooks, because the whole point is to avoid hardware interrupts
> > from firing using these parameters.
> >
> > Propose new mechanisms to control NAPI behavior if you want.
> I'll remove the ixgbe code if that is what you want.  It may be a month 
> or so before I can get to it though since I am slammed with work so if 
> you are in a hurry for it you might want to work with Jeff Kirsher to 
> have the code removed.

Alex- I will work on this to resolve the issues the Ben and Dave have
pointed out.

> 
> As far as this current patch goes I honestly don't have the time to add 
> or rewrite yet another ethtool interface so I will probably just see 
> about dropping the ethtool portion of this patch and update the 
> description in order to make it acceptable.
> 
> Thanks,
> 
> Alex



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