From owner-freebsd-net  Fri Jul 28 14:50: 4 2000
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From: Archie Cobbs <archie@whistle.com>
Message-Id: <200007282148.OAA27647@bubba.whistle.com>
Subject: Re: sub-optimal tcp_ouput() performance in the face of ENOBUFS
In-Reply-To: <20394.964820589@verdi.nethelp.no> from "sthaug@nethelp.no" at "Jul
 28, 2000 11:43:09 pm"
To: sthaug@nethelp.no
Date: Fri, 28 Jul 2000 14:48:45 -0700 (PDT)
Cc: archie@whistle.com, silby@silby.com, freebsd-net@FreeBSD.ORG,
	jlemon@FreeBSD.ORG
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sthaug@nethelp.no writes:
> > I understand the scenario described by the commit message. What
> > I don't understand about this commit is this: suppose the exact
> > same scenario happens, except that instead of ip_output() returning
> > ENOBUFS, it returns zero, BUT the packet is dropped anyway because
> > of (say) an Ethernet collision.
> 
> A normal Ethernet collision does *not* result in a dropped packet -
> simply a packet which is transmitted a few microseconds later by the
> Ethernet hardware.
> 
> If the packet has not been successfully transmitted in 16 attempts,
> it is indeed dropped - but this is (or should be!) an extremely rare
> event.

Yes, that's what I meant -- 16 collisions or whatever. The point is
that the packet gets dropped, it doesn't matter how.

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com


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