From: Manfred Spraul <manfred@colorfullife.com>
To: paulmck@linux.vnet.ibm.com
Cc: linux-kernel@vger.kernel.org, cl@linux-foundation.org,
mingo@elte.hu, akpm@linux-foundation.org, dipankar@in.ibm.com,
josht@linux.vnet.ibm.com, schamp@sgi.com, niv@us.ibm.com,
dvhltc@us.ibm.com, ego@in.ibm.com, laijs@cn.fujitsu.com,
rostedt@goodmis.org, peterz@infradead.org,
penberg@cs.helsinki.fi, andi@firstfloor.org
Subject: Re: [PATCH, RFC] v4 scalable classic RCU implementation
Date: Tue, 16 Sep 2008 19:48:00 +0200 [thread overview]
Message-ID: <48CFF150.8070400@colorfullife.com> (raw)
In-Reply-To: <20080916173012.GC6717@linux.vnet.ibm.com>
Paul E. McKenney wrote:
>
>> That means an O(NR_CPUS) loop with disabled local interrupts :-(
>> Is that correct?
>>
>
> With the definition of "O()" being the worst-case execution time, yes.
> But this worst case could only happen when the system was mostly idle,
> in which case the added overhead should not be too horribly bad.
No: "was mostly running cpu_idle()". A cpu_idle() cpu could execute lots
of irqs and softirqs.
So the worst case would be a system with 1 cpu/node for reserved for irq
handling.
The "idle" cpu would be always in no_hz mode, even though it might be
100% busy handling irqs.
The remaning cpus might be 100% busy handling user space.
And every quiescent state will end up in that O(NR_CPUS) loop.
--
Manfred
next prev parent reply other threads:[~2008-09-16 17:47 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-21 23:43 [PATCH, RFC, tip/core/rcu] scalable classic RCU implementation Paul E. McKenney
2008-08-22 4:37 ` Ingo Molnar
2008-08-22 13:47 ` Paul E. McKenney
2008-08-22 17:22 ` Paul E. McKenney
2008-08-22 18:16 ` Josh Triplett
2008-08-23 16:07 ` Ingo Molnar
2008-08-24 2:44 ` Paul E. McKenney
2008-08-22 23:29 ` Josh Triplett
2008-08-23 1:53 ` Paul E. McKenney
2008-08-25 22:02 ` Josh Triplett
2008-08-26 16:05 ` Paul E. McKenney
2008-08-27 0:38 ` Josh Triplett
2008-08-27 18:34 ` Paul E. McKenney
2008-08-27 20:23 ` Josh Triplett
2008-08-27 20:41 ` Paul E. McKenney
2008-08-25 10:34 ` Peter Zijlstra
2008-08-25 15:16 ` Paul E. McKenney
2008-08-25 15:26 ` Peter Zijlstra
2008-08-27 18:28 ` Paul E. McKenney
2008-08-24 8:08 ` Manfred Spraul
2008-08-24 16:32 ` Paul E. McKenney
2008-08-24 18:25 ` Manfred Spraul
2008-08-24 21:19 ` Paul E. McKenney
2008-08-25 0:07 ` [PATCH, RFC, tip/core/rcu] v2 " Paul E. McKenney
2008-08-30 0:49 ` [PATCH, RFC, tip/core/rcu] v3 " Paul E. McKenney
2008-08-30 9:33 ` Peter Zijlstra
2008-08-30 14:10 ` Paul E. McKenney
2008-08-30 15:40 ` Peter Zijlstra
2008-08-30 19:38 ` Paul E. McKenney
2008-09-02 13:26 ` Mathieu Desnoyers
2008-09-02 13:41 ` Peter Zijlstra
2008-09-02 14:55 ` Paul E. McKenney
2008-08-30 9:58 ` Lai Jiangshan
2008-08-30 13:32 ` Manfred Spraul
2008-08-30 14:34 ` Paul E. McKenney
2008-08-31 10:58 ` Manfred Spraul
2008-08-31 17:20 ` Paul E. McKenney
2008-08-31 17:45 ` Manfred Spraul
2008-08-31 17:55 ` Paul E. McKenney
2008-08-31 18:18 ` Manfred Spraul
2008-08-31 19:23 ` Paul E. McKenney
2008-08-30 14:29 ` Paul E. McKenney
2008-09-01 9:38 ` Andi Kleen
2008-09-02 1:05 ` Paul E. McKenney
2008-09-02 6:18 ` Andi Kleen
2008-09-05 15:29 ` [PATCH, RFC] v4 " Paul E. McKenney
2008-09-05 19:33 ` Andrew Morton
2008-09-05 23:04 ` Paul E. McKenney
2008-09-05 23:52 ` Andrew Morton
2008-09-06 4:16 ` Paul E. McKenney
2008-09-06 16:37 ` Manfred Spraul
2008-09-07 17:25 ` Paul E. McKenney
2008-09-07 10:18 ` [RFC, PATCH] Add a CPU_STARTING notifier (was: Re: [PATCH, RFC] v4 scalable classic RCU implementation) Manfred Spraul
2008-09-07 11:07 ` Andi Kleen
2008-09-07 19:46 ` Paul E. McKenney
2008-09-15 16:02 ` [PATCH, RFC] v4 scalable classic RCU implementation Paul E. McKenney
2008-09-16 16:52 ` Manfred Spraul
2008-09-16 17:30 ` Paul E. McKenney
2008-09-16 17:48 ` Manfred Spraul [this message]
2008-09-16 18:22 ` Paul E. McKenney
2008-09-21 11:09 ` Manfred Spraul
2008-09-21 21:14 ` Paul E. McKenney
2008-09-23 23:53 ` [PATCH, RFC] v6 " Paul E. McKenney
2008-09-25 7:26 ` Ingo Molnar
2008-09-25 14:05 ` Paul E. McKenney
2008-09-25 7:29 ` Ingo Molnar
2008-09-25 14:18 ` Paul E. McKenney
2008-10-10 16:09 ` [PATCH, RFC] v7 " Paul E. McKenney
2008-10-12 15:52 ` Manfred Spraul
2008-10-12 22:46 ` Paul E. McKenney
2008-10-13 18:03 ` Manfred Spraul
2008-10-15 1:11 ` Paul E. McKenney
2008-10-15 8:13 ` Manfred Spraul
2008-10-15 15:26 ` Paul E. McKenney
2008-10-22 18:41 ` Manfred Spraul
2008-10-22 21:02 ` Paul E. McKenney
2008-10-22 21:24 ` Manfred Spraul
2008-10-27 16:45 ` Paul E. McKenney
2008-10-27 19:48 ` Manfred Spraul
2008-10-27 23:52 ` Paul E. McKenney
2008-10-28 5:30 ` Manfred Spraul
2008-10-28 15:17 ` Paul E. McKenney
2008-10-28 17:21 ` Manfred Spraul
2008-10-28 17:35 ` Paul E. McKenney
2008-10-17 8:34 ` Gautham R Shenoy
2008-10-17 15:35 ` Gautham R Shenoy
2008-10-17 15:46 ` Paul E. McKenney
2008-10-17 15:43 ` Paul E. McKenney
2008-12-08 18:42 ` Paul E. McKenney
2008-11-02 20:10 ` Manfred Spraul
2008-11-03 20:33 ` Paul E. McKenney
2008-11-05 19:48 ` Manfred Spraul
2008-11-05 21:27 ` Paul E. McKenney
2008-11-15 23:20 ` [PATCH, RFC] v8 " Paul E. McKenney
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