Date: Tue, 17 Apr 2001 19:34:56 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: "E.B. Dreger" <eddy+public+spam@noc.everquick.net> Cc: Alfred Perlstein <bright@wintelcom.net>, Greg Lehey <grog@lemis.com>, "Justin T. Gibbs" <gibbs@scsiguy.com>, Doug Barton <DougB@DougBarton.net>, "current @ freebsd . org" <current@FreeBSD.ORG> Subject: Re: Kernel preemption, yes or no? (was: Filesystem gets a huge performance boost) Message-ID: <200104180234.f3I2Yuq17047@earth.backplane.com> References: <Pine.LNX.4.20.0104180211450.14449-100000@www.everquick.net>
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:IIRC, didn't the NT driver for some NIC (Intel?) switch to polling,
:anyway, under heavy load? The reasoning being that you _know_ that you're
:going to get something... why bother an IRQ hit?
:
:That said, IRQ distribution sounds like a good thing for the general case.
Under a full load polling would work just as well as an interrupt.
With NT for the network tests they hardwired each NIC to a particular
CPU. I don't know if they did any polling or not.
:> If you have one NIC then obviously you can't take multiple interrupts
:> for that one NIC on different cpu's. No great loss, you generally don't
:> want to do that anyway.
:
:Actually, I should think that one would _want_ to serialize traffic for a
:given NIC. (I'm ignoring when one trunks NICs... speaking of which,
:anyone have info on 802.3ad? ;-) Otherwise, one ends up with a race that
:[potentially] screws up packet sequence.
:
:Eddy
Yes. Also NICs usually have circular buffers for packets so, really,
only one cpu can be processing a particular NIC's packets at any given
moment.
-Matt
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