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Date:      Tue, 20 Nov 2012 19:08:33 -0600
From:      khatfield@socllc.net
To:        Alfred Perlstein <bright@mu.org>
Cc:        Barney Cordoba <barney_cordoba@yahoo.com>, Jim Thompson <jim@netgate.com>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   Re: FreeBSD boxes as a 'router'...
Message-ID:  <832757660.33924.1353460119408@238ae4dab3b4454b88aea4d9f7c372c1.nuevasync.com>
In-Reply-To: <50AC08EC.8070107@mu.org>
References:  <1353448328.76219.YahooMailClassic@web121602.mail.ne1.yahoo.com> <E1F4816E-676C-4630-9FA1-817F737D007D@netgate.com> <50AC08EC.8070107@mu.org>

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Barney - I would certainly love to see some real evidence to backup such a =
ridiculous claim.

I agree here as well with Jim. I have a ton of experience with and without.=
 I haven't done enough testing with FreeBSD 9 to state 100% but I can state=
 that extensive testing and filtering traffic (specifically high PPS DDoS t=
raffic) and polling is a requirement in certain situations.=20

It should not be required for normal traffic, certainly under 200Mbps but i=
n no way should polling be discounted completely. Tuning Intel NICs works t=
o an extent but offloading everything to the NIC without polling is a sure =
fire way to live-lock a system in high PPS situations.

So anyway, I stick to my original assessment that it can be iffy depending =
on volume and scenario but I will also state that throwing polling out comp=
letely discounts one of the strengths easily available on FreeBSD. That wou=
ld be short-sighted, in my opinion.

My recommendation is to use polling if you begin seeing lag or live-lock. I=
n general use it isn't required but I assure you it can be extremely helpfu=
l or detrimental. It all depends on the application of the system and the t=
ype of workload it has.

-Kevin



On Nov 20, 2012, at 4:49 PM, "Alfred Perlstein" <bright@mu.org> wrote:

> On 11/20/12 2:42 PM, Jim Thompson wrote:
>> On Nov 20, 2012, at 3:52 PM, Barney Cordoba <barney_cordoba@yahoo.com> w=
rote:
>>=20
>>> Anyone who even mentions polling should be discounted altogether. Polli=
ng
>>> had value when you couldn't control the interrupt delays; but interrupt
>>> moderation allows you to pace the interrupts any way you like without
>>> the inefficiencies of polling.
>> You're entitled to your opinion, but experimental results have tended to=
 show yours incorrect.
>>=20
>> Jim
> Agree with Jim.  If you want pure packet performance you burn a core to r=
un a polling loop.
>=20
> -Alfred



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