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Date:      Tue, 23 Sep 2014 18:40:15 +0200
From:      Luigi Rizzo <rizzo@iet.unipi.it>
To:        "Alexander V. Chernikov" <melifaro@freebsd.org>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, Elof Ofel <elofu17@hotmail.com>
Subject:   Re: How do I balance bandwidth over several virtual NICs?
Message-ID:  <CA%2BhQ2%2Bh8pnoUeh0big1JrYMrVkXYi=Txkh2Ua4i-=tCarq4rdQ@mail.gmail.com>
In-Reply-To: <5421A1AF.9000800@FreeBSD.org>
References:  <DUB125-W13FDC584F5DF9881CF5FDEBCB30@phx.gbl> <CA%2BP_MZGA_uz_H_QsB%2BdgXEgbXNCjv7w-OToKby=ww%2BvKgnU4_Q@mail.gmail.com> <DUB125-W851F972702452D9809C8E5BCB30@phx.gbl> <CAJ-Vmo=NGGkOkPWQKZ=3gA3vYYyM2kcjd3m85ymdJY3q4ixxLw@mail.gmail.com> <5421310C.5010406@FreeBSD.org> <CAJ-VmomamPVwja2Tgfi46EBu8E5Hohr6FcshsOkDeycEvGV51Q@mail.gmail.com> <CA%2BhQ2%2BhU6XwaeyqdcseL9uusmKfyG4Ko7TwvsZwU=r1cUyCw1w@mail.gmail.com> <54218EF4.6090102@FreeBSD.org> <20140923154610.GD84074@onelab2.iet.unipi.it> <CAJ-VmokS=A3TFb4K_dyvXBYuFoa94cBMXezVJ7MkttPe9mK-1w@mail.gmail.com> <5421A1AF.9000800@FreeBSD.org>

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On Tuesday, September 23, 2014, Alexander V. Chernikov <melifaro@freebsd.org>
wrote:

> On 23.09.2014 20:00, Adrian Chadd wrote:
>
>> Ah, this behaviour.
>>
>> It's called DROP_EN on the intel igb / ixgbe hardware. Grep the
>> drivers for that particular register bit/setting.
>>
>> Set that bit for an RX queue and it'll instruct the MAC to drop frames
>> destined if that RX ring is full to it and keep receiving on the other
>> rings. Otherwise yes, receiving on that ring with the ring full cuases
>> the MAC to stop receiving on all rings until that ring has free space.
>>
>> You flip this on with ixgbe and igb by disabling tx/rx flowcontrol
>> (sysctl dev.ix|igb.X.fc=0) before configuring the interface.
>>
> Oh, cool.
> Yet another reason to turn flow control off by default.


Or at least decouple the two features.

Cheers
Luigi


>
>>
>>
>> -a
>>
>>
>

-- 
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 Prof. Luigi RIZZO, rizzo@iet.unipi.it  . Dip. di Ing. dell'Informazione
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 TEL      +39-050-2211611               . via Diotisalvi 2
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