From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: dave.taht@bufferbloat.net, netdev@vger.kernel.org,
nichols@pollere.com, van@pollere.net,
codel@lists.bufferbloat.net, ycheng@google.com,
mattmathis@google.com, therbert@google.com,
shemminger@vyatta.com, nanditad@google.com
Subject: Re: [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.
next prev parent reply other threads:[~2012-05-12 21:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-12 13:32 [PATCH net-next] codel: use Newton method instead of sqrt() and divides 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 22:33 ` David Miller
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