netdev - Re: [net-next-2.6 PATCH] net: fast consecutive name allocation

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Date:	Fri, 13 Nov 2009 16:04:45 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Octavian Purdila <opurdila@...acom.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [net-next-2.6 PATCH] net: fast consecutive name allocation

On Fri, 13 Nov 2009 07:20:19 +0200
Octavian Purdila <opurdila@...acom.com> wrote:

> On Friday 13 November 2009 07:01:14 you wrote:
> > This patch speeds up the network device name allocation for the case
> > where a significant number of devices of the same type are created
> > consecutively.
> > 
> > Tests performed on a PPC750 @ 800Mhz machine with per device sysctl
> > and sysfs entries disabled:
> > 
> > Without the patch           With the patch
> > 
> > real    0m 43.43s	    real    0m 0.49s
> > user    0m 0.00s	    user    0m 0.00s
> > sys     0m 43.43s	    sys     0m 0.48s

Since the main overhead here is building the bitmap table used in the
name scan. Why not mantain the bitmap table between calls by
implementing a rbtree with prefix -> bitmap.
The tree would have to be limited and per namespace but then you
could handle the general case of adding a device, then its vlans,
then another device, ...


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