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From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: dave.taht@bufferbloat.net, nanditad@google.com,
	netdev@vger.kernel.org, codel@lists.bufferbloat.net,
	ycheng@google.com, shemminger@vyatta.com, mattmathis@google.com
Subject: Re: [Codel] [PATCH net-next] codel: use Newton method instead of sqrt() and divides
Date: Sat, 12 May 2012 17:52:17 -0400 (EDT)	[thread overview]
Message-ID: <20120512.175217.1632102067268101115.davem@davemloft.net> (raw)
In-Reply-To: <1336859324.31653.1385.camel@edumazet-glaptop>

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Sat, 12 May 2012 23:48:44 +0200

> On Sat, 2012-05-12 at 16:45 -0400, David Miller wrote:
>> Using a u16 would also work for me.
> 
> I tried it but it gives noticeable errors for count > 16000, and no
> speed gain.
 ...
> And if a flow is really agressive, count can grow above 10^6
> 
>> > By the way, gcc on x86 generates nice "and 0xfffffffe,%eax" instruction
>> > for (vars->rec_inv_sqrt << 1).
>> 
>> Yeah but what do stores of ->rec_inv_sqrt look like?
> 
> The load is "shr %edi" as in :
> and the store an "or %ecx,%esi"

Ok, fair enough.

  reply	other threads:[~2012-05-12 21:54 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-12 13:32 Eric Dumazet
2012-05-12 19:52 ` David Miller
2012-05-12 20:40   ` Eric Dumazet
2012-05-12 20:45     ` David Miller
2012-05-12 21:48       ` Eric Dumazet
2012-05-12 21:52         ` David Miller [this message]
2012-05-13  7:23           ` Eric Dumazet
2012-05-14  5:46             ` Andrew McGregor
2012-05-14  6:00               ` dave taht
2012-05-14  6:17                 ` Eric Dumazet
2012-05-14  6:33                   ` dave taht
2012-05-14  6:47                     ` dave taht
2012-05-14  6:51                       ` Roger Jørgensen
2012-05-14  8:23                         ` Eric Dumazet
2012-05-14  8:50                           ` dave taht
2012-05-14  9:03                             ` Eric Dumazet
2012-05-14 11:34                           ` Roger Jørgensen
2012-05-14 11:56                             ` Eric Dumazet
2012-05-14 15:05                             ` Dave Taht
2012-05-14 18:31                               ` Roger Jørgensen
2012-05-14 22:33             ` David Miller

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