netdev - RE: [PATCH net-next] net: sched: use no more than one page in struct fw

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D0F6DF5AE@AcuExch.aculab.com>
Date:	Mon, 17 Mar 2014 15:43:23 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Eric Dumazet' <eric.dumazet@...il.com>
CC:	Thomas Graf <tgraf@...g.ch>, David Miller <davem@...emloft.net>,
	"John Fastabend" <john.fastabend@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next] net: sched: use no more than one page in
 struct fw_head

From: Eric Dumazet ...
> > or use a 'modulo 2^n-1 reduction':
> > 	handle = (handle & 0x3ffff) + (handle >> 18);
> > 	do
> > 		handle = (handle & 0x1ff) + (handle >> 9);
> > 	while (handle > 0x1ffu);
> 
> All these tricks were needed 20 years ago.
> 
> Even Thomas laptop can do a divide faster than this loop.

The nios cpu on my fpga can't :-)
OTOH I wouldn't run Linux on a 100Mhz cpu.

	David