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From: Andi Kleen <andi@firstfloor.org>
To: Juliusz Chroboczek <Juliusz.Chroboczek@pps.jussieu.fr>
Cc: Andi Kleen <andi@firstfloor.org>, netdev@vger.kernel.org
Subject: Re: [PATCH] Stochastic Fair Blue queue discipline
Date: Wed, 9 Apr 2008 19:49:54 +0200	[thread overview]
Message-ID: <20080409174954.GD30885@one.firstfloor.org> (raw)
In-Reply-To: <7ik5j7ghgh.fsf@lanthane.pps.jussieu.fr>

> Random32 is initialised from get_random_bytes; so the per-cpu
> pseudo-random sequences should be uncorrelated.  I fail to see how an
> arbitrary interleaving of uncorrelated good pseudo-random sequences
> can fail to be good.

They are not necessarily uncorreleated, especially on platforms
which do have poor entropy support and when your initialization happens
at boot time. Take a look at how the random pool starts in random.c.

> 
> Looking at line 448 of sch_sfq.c in Linus' current HEAD, I see that
> somebody else thinks the same as I do.  So please let me know if sfq
> needs fixed, or whether I can use net_random in sfb.

A lot of people get this wrong, but this doesn't mean that the
problem should be readded in new code again.

-Andi

  reply	other threads:[~2008-04-09 17:45 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-07 22:37 [PATCH] Stochastic Fair Blue queue discipline Juliusz Chroboczek
2008-04-08  0:04 ` Patrick McHardy
2008-04-08  0:56   ` Patrick McHardy
2008-04-08 15:28   ` Juliusz Chroboczek
2008-04-08  8:20 ` Andi Kleen
2008-04-08 12:11   ` Patrick McHardy
2008-04-08 15:39     ` Juliusz Chroboczek
2008-04-08 15:45       ` Patrick McHardy
2008-04-09 15:48         ` Juliusz Chroboczek
2008-04-09 16:00           ` Patrick McHardy
2008-04-08 15:38   ` Juliusz Chroboczek
2008-04-08 16:32     ` Andi Kleen
2008-04-08 17:35       ` Juliusz Chroboczek
2008-04-08 17:53         ` Andi Kleen
2008-04-09 15:45           ` Juliusz Chroboczek
2008-04-09 17:49             ` Andi Kleen [this message]
2008-04-10  1:23               ` Patrick McHardy
2008-04-10  1:38                 ` Patrick McHardy
2008-04-10 11:17                   ` Juliusz Chroboczek
2008-04-11 13:07                     ` Patrick McHardy
2008-04-10 14:04                   ` Stephen Hemminger
2008-04-10  7:36                 ` Andi Kleen
2008-04-08 16:44 ` Patrick McHardy

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