From: Benjamin LaHaise <bcrl@lhnet.ca>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH/RFC] make unregister_netdev() delete more than 4 interfaces per second
Date: Sun, 18 Oct 2009 12:13:57 -0400 [thread overview]
Message-ID: <20091018161356.GA23395@kvack.org> (raw)
In-Reply-To: <4ADA98EE.9040509@gmail.com>
On Sun, Oct 18, 2009 at 06:26:22AM +0200, Eric Dumazet wrote:
> Unfortunatly this slow down fast path by an order of magnitude.
>
> atomic_dec() is pretty cheap (and eventually could use a per_cpu thing,
> now we have a new and sexy per_cpu allocator), but atomic_dec_and_test()
> is not that cheap and more important forbids a per_cpu conversion.
dev_put() is not a fast path by any means. atomic_dec_and_test() costs
the same as atomic_dec() on any modern CPU -- the cost is in the cacheline
bouncing and serialisation both require. The case of the device count
becoming 0 is quite rare -- any device with a route on it will never hit
a reference count of 0.
-ben
next prev parent reply other threads:[~2009-10-18 16:13 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-17 22:18 [PATCH/RFC] make unregister_netdev() delete more than 4 interfaces per second Benjamin LaHaise
2009-10-18 4:26 ` Eric Dumazet
2009-10-18 16:13 ` Benjamin LaHaise [this message]
2009-10-18 17:51 ` Eric Dumazet
2009-10-18 18:21 ` Benjamin LaHaise
2009-10-18 19:36 ` Eric Dumazet
2009-10-21 12:39 ` Octavian Purdila
2009-10-21 15:40 ` [PATCH] net: allow netdev_wait_allrefs() to run faster Eric Dumazet
2009-10-21 16:09 ` Eric Dumazet
2009-10-21 16:51 ` Benjamin LaHaise
2009-10-21 19:54 ` Eric Dumazet
2009-10-29 23:07 ` Eric W. Biederman
2009-10-29 23:38 ` Benjamin LaHaise
2009-10-30 1:45 ` Eric W. Biederman
2009-10-30 14:35 ` Benjamin LaHaise
2009-10-30 14:43 ` Eric Dumazet
2009-10-30 23:25 ` Eric W. Biederman
2009-10-30 23:53 ` Benjamin LaHaise
2009-10-31 0:37 ` Eric W. Biederman
2010-08-09 17:23 ` Ben Greear
2010-08-09 17:34 ` Benjamin LaHaise
2010-08-09 17:44 ` Ben Greear
2010-08-09 17:48 ` Benjamin LaHaise
2010-08-09 18:03 ` Ben Greear
2010-08-09 19:59 ` Eric W. Biederman
2010-08-09 21:03 ` Benjamin LaHaise
2010-08-09 21:17 ` Eric W. Biederman
2009-10-21 16:55 ` Octavian Purdila
2009-10-23 21:13 ` Paul E. McKenney
2009-10-24 4:35 ` Eric Dumazet
2009-10-24 5:49 ` Paul E. McKenney
2009-10-24 8:49 ` Eric Dumazet
2009-10-24 13:52 ` Paul E. McKenney
2009-10-24 14:24 ` Eric Dumazet
2009-10-24 14:46 ` Paul E. McKenney
2009-10-24 23:49 ` Octavian Purdila
2009-10-25 4:47 ` Paul E. McKenney
2009-10-25 8:35 ` Eric Dumazet
2009-10-25 15:19 ` Octavian Purdila
2009-10-25 19:28 ` Eric Dumazet
2009-10-24 20:22 ` Stephen Hemminger
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