netdev - Re: Scalability of interface creation and deletion

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Date:	Sun, 08 May 2011 09:06:11 +0100
From:	Alex Bligh <alex@...x.org.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	netdev@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Alex Bligh <alex@...x.org.uk>
Subject: Re: Scalability of interface creation and deletion

Eric,

> By the way, if I change HZ from 1000 to 100 I now have ten times slower
> result :
>
># ip link add link eth0 eth0.103 type vlan id 103
># time ip link del eth0.103
>
> real	0m0.430s
> user	0m0.000s
> sys	0m0.000s
>
> So all this is related to your HZ value, even in a CONFIG_NO_HZ=y
> kernel.

That's very mysterious.

> Alex, I guess you have HZ=250 ?

I have HZ=100. I am basically using the Ubuntu default with
localmodconfig to make compile times sensible.

amb@...tytest:~$ cd kernel/linux-2.6/
amb@...tytest:~/kernel/linux-2.6$ fgrep HZ .config
CONFIG_RCU_FAST_NO_HZ=y
CONFIG_NO_HZ=y
CONFIG_HZ_100=y
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=100
# CONFIG_MACHZ_WDT is not set



-- 
Alex Bligh
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