netdev - Re: [RFC] make per interface sysctl entries configurable

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Message-Id: <200910261724.58541.denys@visp.net.lb>
Date:	Mon, 26 Oct 2009 17:24:58 +0200
From:	Denys Fedoryschenko <denys@...p.net.lb>
To:	Octavian Purdila <opurdila@...acom.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Benjamin LaHaise <bcrl@...et.ca>,
	Stephen Hemminger <shemminger@...tta.com>,
	Cosmin Ratiu <cratiu@...acom.com>, netdev@...r.kernel.org
Subject: Re: [RFC] make per interface sysctl entries configurable

I test it on pppoe with 1k customers. It works flawlessly.

When there is problem on network and i have massive users disconnect and then 
login, the bottleneck is in lock somewhere in creation of sysctl(according 
perf). PPPoE after 200-300 interfaces will start dying, and connection rate 
will drop to 20-50 customers per minute, load average will jump to 70-100 (i 
guess pppd processes waiting their turn). With this patch i am able to 
sustain 200-300 customers / minute login rate and perftop is "clear" now.

Definitely this option is optional, and doesn't cut any functionality by 
default, just giving more choice. And for PPP (pppoe/pptp) NAS it is very 
useful.

On Sunday 25 October 2009 19:54:49 Octavian Purdila wrote:
> RFC patches are attached.
>
> Another possible approach: add an interface flag and use it to decide
> whether we want per interface sysctl entries or not.
>
> Benchmarks for creating 1000 interface (with the ndst module previously
> posted on the list, ppc750 @800Mhz machine):
>
> - without the patches:
>
> real    4m 38.27s
> user    0m 0.00s
> sys     2m 18.90s
>
> - with the patches:
>
> real    0m 0.10s
> user    0m 0.00s
> sys     0m 0.05s
>
> Thanks,
> tavi

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