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Date:      Thu, 8 Oct 2009 22:19:48 +1100 (EST)
From:      Ian Smith <smithi@nimnet.asn.au>
To:        rihad <rihad@mail.ru>
Cc:        freebsd-net@freebsd.org, Eugene Grosbein <eugen@kuzbass.ru>, Robert Watson <rwatson@freebsd.org>, Luigi Rizzo <rizzo@iet.unipi.it>, Julian Elischer <julian@elischer.org>
Subject:   Re: dummynet dropping too many packets
Message-ID:  <20091008212623.D88524@sola.nimnet.asn.au>
In-Reply-To: <4ACCA92A.9070803@mail.ru>
References:  <4AC9E29B.6080908@mail.ru> <20091005123230.GA64167@onelab2.iet.unipi.it> <4AC9EFDF.4080302@mail.ru> <4ACA2CC6.70201@elischer.org> <4ACAFF2A.1000206@mail.ru> <4ACB0C22.4000008@mail.ru> <20091006100726.GA26426@svzserv.kemerovo.su> <4ACB42D2.2070909@mail.ru> <20091006142152.GA42350@svzserv.kemerovo.su> <4ACB6223.1000709@mail.ru> <20091006161240.GA49940@svzserv.kemerovo.su> <alpine.BSF.2.00.0910061804340.50283@fledge.watson.org> <4ACC5563.602@mail.ru> <4ACC56A6.1030808@mail.ru> <alpine.BSF.2.00.0910070957430.58146@fledge.watson.org> <4ACC5DEC.1010006@mail.ru> <alpine.BSF.2.00.0910071036280.58146@fledge.watson.org> <4ACC65A0.7030900@mail.ru> <alpine.BSF.2.00.0910071312420.58146@fledge.watson.org> <4ACC8CC8.8050403@mail.ru> <alpine.BSF.2.00.0910071420290.38033@fledge.watson.org> <4ACCA92A.9070803@mail.ru>

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On Wed, 7 Oct 2009, rihad wrote:

 > Robert Watson wrote:
 > 
 > > I would suggest making just the HZ -> 4000 change for now and see how it
 > > goes.
 > > 
 > OK, I will try testing HZ=4000 tomorrow morning, although I'm pretty sure
 > there still will be some drops.

Even if there are, I'd like to know what (rough) percentage in increased 
interrupt load you experience with HZ=4000 vs 1000 on that beast in your 
application, or of any discernable effects on other running processes?

[Thanks guys for this interesting thread]

 > > > Can someone please say how to increase the "ifnet transmit queue sizes"?
 > > 
 > > Unfortunately, I fear that this is driver-specific, and in the case of bce
 > > requires a recompile.  In the driver init code in if_bce, the following
 > > code appears:
 > > 
 > >         ifp->if_snd.ifq_drv_maxlen = USABLE_TX_BD;
 > >         IFQ_SET_MAXLEN(&ifp->if_snd, ifp->if_snd.ifq_drv_maxlen);
 > >         IFQ_SET_READY(&ifp->if_snd);
 > > 
 > > Which evaluates to a architecture-specific value due to varying pagesize.
 > > You might just try forcing it to 1024.
 > > 
 > I think I'll try this too, if HZ=4000 doesn't help, thanks a lot.
 > In the long run we'll switch to some high-quality 10 GiGE cards.



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