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Date: Fri, 14 Jan 2011 16:04:44 +1100 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Jack Vogel <jfvogel@gmail.com>
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Cc: Charles Owens <cowens@greatbaysoftware.com>, Robin Sommer <robin@icir.org>,
	freebsd-net <freebsd-net@freebsd.org>
Subject: Re: igb watchdog timeouts
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On Thu, 13 Jan 2011, Jack Vogel wrote:

> Polling has seemed to me to be a way around other problems, problems that
> these days
> no longer exist. I remember back in the FreeBSD 6 days having interrupt
> problems which
> of course also led to watchdogs. Polling got rid of that. But now there are
> dedicated
> MULTIPLE interrupts by using MSIX, so that reason for polling is gone.
>
> Of course there can still be advantages, reducing interrupts and hence
> context switches,
> which is why the Linux approach does what it does.

Polling helps, if at all, mainly by reducing interrupts and otherwise
dropping packets (or for tx, not sending packets promptly, so that the
system doesn't become overloaded attempting to not drop packets and
to send packets promptly, according to interrupts).  The last thing
an overloaded system wants is MORE interrupts to tell it that it is
overloaded :-).

Bruce