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

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Date:	Fri, 13 Nov 2009 16:20:50 -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 Sat, 14 Nov 2009 02:14:21 +0200
Octavian Purdila <opurdila@...acom.com> wrote:

> On Saturday 14 November 2009 02:04:45 you wrote:
> > 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, ...
> > 
> 
> I'll do that !
> 
> That was my original intent but I thought it would be too much bloat :) But I 
> see your point, even if it is more complex, its more useful.

There might even be a VM notifier hook that could be used to drop the whole
tree if any memory pressure was felt.

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