From: Eric Dumazet <eric.dumazet@gmail.com>
To: paulmck@linux.vnet.ibm.com
Cc: Octavian Purdila <opurdila@ixiacom.com>,
Benjamin LaHaise <bcrl@lhnet.ca>,
netdev@vger.kernel.org, Cosmin Ratiu <cratiu@ixiacom.com>
Subject: Re: [PATCH] net: allow netdev_wait_allrefs() to run faster
Date: Sat, 24 Oct 2009 10:49:55 +0200 [thread overview]
Message-ID: <4AE2BFB3.3060407@gmail.com> (raw)
In-Reply-To: <20091024054943.GA6638@linux.vnet.ibm.com>
Paul E. McKenney a écrit :
> On Sat, Oct 24, 2009 at 06:35:53AM +0200, Eric Dumazet wrote:
>
>> Maybe we could call it once only, if we had to call 1 times
>> the jiffie delay ?
>
> This could be a very useful approach!
>
> However, please keep in mind that although synchronize_rcu_expedited()
> forces a grace period, it does nothing to speed the invocation of other
> RCU callbacks. In short, synchronize_rcu_expedited() is a faster version
> of synchronize_rcu(), but doesn't necessarily help other synchronize_rcu()
> or call_rcu() invocations.
>
> The reason I point this out is that it looks to me that the code below is
> waiting for some other task which is in turn waiting on a grace period.
> But I don't know this code, so could easily be confused.
>
Normally, we need a synchronize_rcu() calls, but I feel its bit more than really
needed here.
On my dev machine, a synchronize_rcu() lasts between 2 an 12 ms
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.580259] synchronize_net() 4045596 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.588262] synchronize_net() 7769327 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.625014] synchronize_net() 4772052 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.633008] synchronize_net() 7773896 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.669260] synchronize_net() 3958141 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.677259] synchronize_net() 7755817 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.712011] synchronize_net() 2502544 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.720011] synchronize_net() 7767748 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.754259] synchronize_net() 2087946 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.762258] synchronize_net() 7738054 ns
messages:Oct 21 19:13:14 svivoipvnx001-00 kernel: [ 2515.796011] synchronize_net() 3392760 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.808025] synchronize_net() 11814619 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.848010] synchronize_net() 8970220 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.856015] synchronize_net() 7800782 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.893008] synchronize_net() 6650174 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.897012] synchronize_net() 3744808 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.940202] synchronize_net() 8354366 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.952137] synchronize_net() 11693215 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.985010] synchronize_net() 2355970 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2515.989009] synchronize_net() 3771419 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.028137] synchronize_net() 7661195 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.036152] synchronize_net() 7800056 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.083135] synchronize_net() 6774026 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.089145] synchronize_net() 5727189 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.130385] synchronize_net() 10133932 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.134399] synchronize_net() 3773058 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.170136] synchronize_net() 4479194 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.178138] synchronize_net() 7710466 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.217198] synchronize_net() 4323437 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.226206] synchronize_net() 8723108 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.268013] synchronize_net() 6221155 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.280007] synchronize_net() 11719297 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.324008] synchronize_net() 11654511 ns
messages:Oct 21 19:13:15 svivoipvnx001-00 kernel: [ 2516.332009] synchronize_net() 7744182 ns
next prev parent reply other threads:[~2009-10-24 8:50 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
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 [this message]
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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