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

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Message-ID: <20091112222608.79d90e9e@nehalam>
Date:	Thu, 12 Nov 2009 22:26:08 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Octavian Purdila <opurdila@...acom.com>, netdev@...r.kernel.org
Subject: Re: [net-next-2.6 PATCH] net: fast consecutive name allocation

On Fri, 13 Nov 2009 07:12:35 +0100
Eric Dumazet <eric.dumazet@...il.com> wrote:

> Octavian Purdila a écrit :
> > 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
> >>
> > 

No one has give a reasonable use case for this network device name
explosion, what is the benchmark doing this nosense, and how do I
get paid to do it...

But I have to say no for another reason. You cause the kernel to choose
a different name for the case where a device is deleted or renamed.
The old code would find and fill the hole when a new device was added.

Since this is a semantic ABI change, the kind that drives users nuts.

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