Date: Mon, 5 Nov 2012 17:57:48 +0100 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Joe Holden <lists@rewt.org.uk> Cc: Davide Italiano <davide@freebsd.org>, Ryan Stone <rysto32@gmail.com>, FreeBSD Current <current@freebsd.org> Subject: Re: Dynamic Ticks/HZ Message-ID: <20121105165748.GA13098@onelab2.iet.unipi.it> In-Reply-To: <5097E880.8010001@rewt.org.uk> References: <509758B8.1000409@rewt.org.uk> <CACYV=-HwJ1j2-zDtCtuGNKzdFRJhPsZm6vtFXAVyPSabCXvFEQ@mail.gmail.com> <50975F6F.6010907@rewt.org.uk> <CACYV=-Ef5ij7%2BgqDV9oS3xRyD6Yy2mqDyKqqUZZQ-KsWb_3C3A@mail.gmail.com> <5097898C.9080109@rewt.org.uk> <CAFMmRNwR_XxjnRZvxqew77qNnOTGWrRQnhJkg4u2berL8VCVtw@mail.gmail.com> <20121105163654.GA12870@onelab2.iet.unipi.it> <5097E880.8010001@rewt.org.uk>
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On Mon, Nov 05, 2012 at 04:25:36PM +0000, Joe Holden wrote: > Luigi Rizzo wrote: > >On Mon, Nov 05, 2012 at 08:11:41AM -0500, Ryan Stone wrote: > >>On Mon, Nov 5, 2012 at 4:40 AM, Joe Holden <lists@rewt.org.uk> wrote: > >> > >>>doh, running kernel wasn't as GENERIC as I thought it was, looks like > >>>device polling not only breaks dynamic ticks but also reduces rx ability > >>>significantly, exactly 150,000 pps per 1000hz on igb versus 650,000 > >>>without > >>> > >>>Is this a known issue? (and if device polling isn't as useful as it once > >>>was, should it be removed?) > >>> > >>Device polling on modern multiqueue NICs isn't very useful because you're > >>limited to a single thread for handling packets. I have a patch that > >>fixes > >>this that I've let fall by the wayside. > > > >the 150,000 is result of the combination of the default value of > >sysctl kern.polling.burst_max and kern.polling.idle_poll=0 > >(i think this is the default value for the latter). > > > >The 150 was sized for the peak pps on a 100Mbit/s interface, > >back in 2001. You should at least be able to raise the number > >and see what kind of throughput you can achieve. > > > >This said, modern nics also have interrupt moderation so you > >don't really need polling. > > > >cheers > >luigi > Hi Luigi, > > This makes sense, am I likely to achieve better throughput (in the > forwarding path at this point) with netisr rather than polling, > especially as mentioned above the igb does indeed have multiple queues > for rx? at 1Gbit/s you probably don't need multiqueue (I am actually surpised you can only do 650kpps, but perhaps because you are using ipfw and not just doing plain forwarding ?) > On another note, is netmap usable in the forwarding context at all as it > is rather awesome It depends on what you need to do. If you have a v4/v6 router you won't see any advantage (at the moment; there is some work in the pipeline but probably it won't be available before spring). If you just need to implement a firewall to protect the internal network then it is another story and you can use the ipfw on netmap that I posted in august. cheers luigi
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