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From: Ingo Molnar <mingo@elte.hu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Jason Baron <jbaron@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	a.p.zijlstra@chello.nl, mathieu.desnoyers@efficios.com,
	davem@davemloft.net, ddaney.cavm@gmail.com,
	akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs
Date: Wed, 22 Feb 2012 08:53:34 +0100	[thread overview]
Message-ID: <20120222075334.GA25053@elte.hu> (raw)
In-Reply-To: <20120222073251.GB17291@elte.hu>


* Ingo Molnar <mingo@elte.hu> wrote:

> But it is fundamentally mixing execution and *data type* and 
> it is not conveying the build time bias properly.
> 
> So the best high level naming would be something like:
> 
> 	struct static_condition static_flag = STATIC_COND_FALSE;
> 
> 
> 	if (very_unlikely(&static_flag)) {
> 		...
> 	}
> 
> 	...
> 
> 	static_cond_inc(&static_flag);
> 	...
> 	static_cond_dec(&static_flag);

Btw., I think the modification path could also carry the high 
cost of modification (stopping all cpus, modifying code, etc.).

This could be done via:

	static_cond_slow_inc(&static_flag);
	...
	static_cond_slow_dec(&static_flag);

And if a developer does not notice that 'slow' implies a 
performance cost, then he probably would have doubly missed this 
aspect of jump_label_inc()/jump_label_dec().

Thanks,

	Ingo

  reply	other threads:[~2012-02-22  7:53 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-21 20:02 [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs Jason Baron
2012-02-21 20:02 ` [PATCH 01/10] jump label: Add a WARN() if jump label key count goes negative Jason Baron
2012-02-29 10:13   ` [tip:perf/core] " tip-bot for Jason Baron
2012-02-21 20:02 ` [PATCH 02/10] jump label: fix compiler warning Jason Baron
2012-02-29 10:14   ` [tip:perf/core] jump label: Fix " tip-bot for Jason Baron
2012-02-21 20:03 ` [PATCH 03/10] jump label: introduce very_unlikely() Jason Baron
2012-02-21 20:03 ` [PATCH 04/10] jump label: introduce very_likely() Jason Baron
2012-02-21 20:03 ` [PATCH 05/10] perf: update to use 'very_unlikely()' Jason Baron
2012-02-21 20:03 ` [PATCH 06/10] tracepoints: update to use very_unlikely() Jason Baron
2012-02-21 20:03 ` [PATCH 07/10] sched: update to use very_[un]likely() Jason Baron
2012-02-21 20:03 ` [PATCH 08/10] kvm: update to use very_unlikely() Jason Baron
2012-02-21 20:03 ` [PATCH 09/10] net: " Jason Baron
2012-02-21 20:03 ` [PATCH 10/10] jump label: Add docs better explaining the whole jump label mechanism Jason Baron
2012-02-29 10:15   ` [tip:perf/core] static keys: Add docs better explaining the whole 'struct static_key' mechanism tip-bot for Jason Baron
2012-02-21 20:09 ` [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs H. Peter Anvin
2012-02-21 20:20   ` Jason Baron
2012-02-21 20:39     ` Steven Rostedt
2012-02-21 21:10       ` H. Peter Anvin
2012-02-21 21:16         ` Mathieu Desnoyers
2012-02-21 21:11       ` Mathieu Desnoyers
2012-02-22  7:32       ` Ingo Molnar
2012-02-22  7:53         ` Ingo Molnar [this message]
2012-02-22  8:01           ` H. Peter Anvin
2012-02-22  8:18             ` Ingo Molnar
2012-02-22  8:58               ` [PATCH] static keys: Introduce 'struct static_key', very_[un]likely(), static_key_slow_[inc|dec]() Ingo Molnar
2012-02-29 10:16                 ` [tip:perf/core] static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]() tip-bot for Ingo Molnar
2012-02-22  9:03               ` [PATCH] jump labels: Explain the .config option better Ingo Molnar
2012-02-22 15:08               ` [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs H. Peter Anvin
2012-02-22 15:51                 ` Ingo Molnar
2012-02-22 21:33               ` Paul Mackerras
2012-02-23 10:02                 ` Ingo Molnar
2012-02-23 16:21                   ` Jason Baron
2012-02-23 17:10                     ` H. Peter Anvin
2012-02-24  9:11                     ` Ingo Molnar
2012-02-23 17:18                   ` Linus Torvalds
2012-02-23 22:33                     ` Ingo Molnar
2012-02-23 22:39                       ` Ingo Molnar
2012-02-23 22:44                         ` Steven Rostedt
2012-02-23 23:18                         ` Mathieu Desnoyers
2012-02-24  2:25                           ` Jason Baron
2012-02-24  9:08                             ` Ingo Molnar
2012-02-24 15:35                               ` Jason Baron
2012-02-27  7:40                                 ` Ingo Molnar
2012-02-24 15:51                               ` Mathieu Desnoyers
2012-02-24 16:06                               ` Steven Rostedt
2012-02-24  7:52                         ` static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]() Ingo Molnar
2012-02-24  7:59                           ` [PATCH] " Ingo Molnar
2012-02-24  7:54                         ` [PATCH] static keys: Add docs better explaining the whole 'struct static_key' mechanism Ingo Molnar
2012-02-23 22:45                       ` [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs Linus Torvalds
2012-02-24  8:04                         ` Ingo Molnar
2012-02-24  2:42                       ` Jason Baron
2012-02-21 20:21   ` Steven Rostedt
2012-02-21 21:11     ` H. Peter Anvin
2012-02-22  6:50   ` Ingo Molnar
2012-02-22  7:03     ` H. Peter Anvin
2012-02-22  7:25       ` Ingo Molnar
2012-02-22  7:35         ` H. Peter Anvin
2012-02-22  7:48           ` Ingo Molnar
2012-02-22  7:55             ` H. Peter Anvin
2012-02-22  8:06               ` Ingo Molnar
2012-02-22 13:22                 ` Steven Rostedt
2012-02-22 13:34                   ` Ingo Molnar
2012-02-22 13:54                     ` Steven Rostedt
2012-02-22 14:20                       ` Mathieu Desnoyers
2012-02-22 14:36                         ` Steven Rostedt
2012-02-22 14:56                       ` Ingo Molnar
2012-02-22 15:11                         ` H. Peter Anvin
2012-02-22 15:11                         ` Peter Zijlstra
2012-02-22 15:47                           ` Ingo Molnar
2012-02-22 15:12                         ` Steven Rostedt
2012-02-22 15:15                           ` H. Peter Anvin
2012-02-22 15:19                           ` H. Peter Anvin
2012-02-22 15:42                           ` Jason Baron
2012-02-22 15:54                             ` Steven Rostedt
2012-02-22 15:56                               ` Jason Baron
2012-02-22 16:08                                 ` Steven Rostedt
2012-02-22 15:19                         ` Jason Baron
2012-02-22 15:40                           ` H. Peter Anvin
2012-02-22 15:13                       ` Peter Zijlstra
2012-02-22 15:32                         ` Peter Zijlstra
2012-02-22 17:14                           ` Richard Henderson
2012-02-22 18:28                             ` H. Peter Anvin
2012-02-22 18:58                             ` Jason Baron
2012-02-22 19:10                               ` H. Peter Anvin

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