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Message-ID: <F57561A93EFF5E88729A8D53@nimrod.local>
Date: Sun, 08 May 2011 10:35:02 +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,
--On 8 May 2011 09:12:22 +0200 Eric Dumazet <eric.dumazet@...il.com> wrote:
> By the way, if I change HZ from 1000 to 100 I now have ten times slower
> result :
I repeated that test here. With HZ set to 1000 I got a total time of
4.022 seconds to remove 100 interfaces, of which:
Total 3.03808 Usage 199 Average 0.01527 elsewhere
Total 0.93992 Usage 200 Average 0.00470 synchronizing
as opposed to a total of 27.917 seconds with HZ set to 100, of which
Total 18.98515 Usage 199 Average 0.09540 elsewhere
Total 8.77581 Usage 200 Average 0.04388 synchronizing
Not quite a factor of 10 improvement, but nearly.
I have CONFIG_RCU_FAST_NO_HZ=y
I suspect this may just mean an rcu reader holds the rcu_read_lock
for a jiffies related time. Though I'm having difficulty seeing
what that might be on a system where the net is in essence idle.
--
Alex Bligh
--
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