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From: Frederic Weisbecker <fweisbec@gmail.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Li Zefan <lizf@cn.fujitsu.com>
Subject: Re: [RFC PATCH 05/10] ftrace: Drop buffer check in function profiler callbacks
Date: Sat, 30 Jan 2010 21:47:38 +0100	[thread overview]
Message-ID: <20100130204737.GF5675@nowhere> (raw)
In-Reply-To: <4B5D3779.2040807@cn.fujitsu.com>

On Mon, Jan 25, 2010 at 02:17:29PM +0800, Lai Jiangshan wrote:
> Frederic Weisbecker wrote:
> > Drop the null check on hlist->hash. It is wasteful because
> > we don't register the tracer if the buffer allocation failed,
> > and the memory barrier in register_ftrace_graph() ensure it
> > is visible to the callbacks right away.
> > 
> 
> When it is on a cpu which is just came up, hlist->hash is not
> allocated either.
> 
> See ftrace_profile_init().
> 
> function_profile_call(), profile_graph_entry() and profile_graph_return()
> on a just online cpu are wasteful. I think we need call
> ftrace_profile_init_cpu()(if ftrace_profile_enabled=1) when CPU_UP_PREPARE.



May be yeah, or perhaps we should play with cpu_possible_mask()
instead of cpu_online. Whatever, the patch is also buggy for the reasons
given by Steve, I'm going to drop it until we have a sane implementation
of synchronize_preempted_tasks().


  reply	other threads:[~2010-01-30 20:47 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-22  1:16 [RFC PATCH 00/10] Ftrace functions hashlist Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 01/10] ftrace: Generalize the function hashlist from function profiler Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 02/10] ftrace: Ensure tracing has really stopped before leaving unregister_ftrace_graph Frederic Weisbecker
2010-01-22  1:51   ` Steven Rostedt
2010-01-22  2:04     ` Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 03/10] ftrace: Drop the ftrace_profile_enabled checks in tracing hot path Frederic Weisbecker
2010-01-22  2:05   ` Steven Rostedt
2010-01-22  2:28     ` Mathieu Desnoyers
2010-01-22  3:12       ` Steven Rostedt
2010-01-22  4:09         ` Mathieu Desnoyers
2010-01-22  4:52           ` Steven Rostedt
2010-01-22 12:34             ` Mathieu Desnoyers
2010-01-22 14:54               ` Masami Hiramatsu
2010-01-25 20:58               ` Frederic Weisbecker
2010-01-25 22:14                 ` Masami Hiramatsu
2010-01-26  0:41                   ` Frederic Weisbecker
2010-01-26  1:13                     ` Mathieu Desnoyers
2010-01-26  1:37                       ` Masami Hiramatsu
2010-01-27 21:55                         ` [PATCH tracing/kprobes] kprobes: Disable booster when CONFIG_PREEMPT=y Masami Hiramatsu
2010-01-28  1:08                           ` Mathieu Desnoyers
2010-01-28  4:21                           ` Ananth N Mavinakayanahalli
2010-01-29  9:21                           ` Ingo Molnar
2010-01-29 11:30                             ` Peter Zijlstra
2010-01-29 14:52                             ` Masami Hiramatsu
2010-01-29 17:08                               ` Mathieu Desnoyers
2010-01-29 17:15                                 ` Peter Zijlstra
2010-01-29 17:27                                   ` Mathieu Desnoyers
2010-01-29 17:32                                     ` Masami Hiramatsu
2010-01-22  2:43     ` [RFC PATCH 03/10] ftrace: Drop the ftrace_profile_enabled checks in tracing hot path Frederic Weisbecker
2010-01-22  3:05       ` Steven Rostedt
2010-01-25 20:52         ` Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 04/10] ftrace: Ensure buffers are visibles to tracing callbacks right away Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 05/10] ftrace: Drop buffer check in function profiler callbacks Frederic Weisbecker
2010-01-25  6:17   ` Lai Jiangshan
2010-01-30 20:47     ` Frederic Weisbecker [this message]
2010-01-22  1:16 ` [RFC PATCH 06/10] ftrace: Release the function hlist if we don't need it anymore Frederic Weisbecker
2010-01-25  6:41   ` Lai Jiangshan
2010-01-30 21:14     ` Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 07/10] ftrace: Make the function hashlist concurrently usable Frederic Weisbecker
2010-01-22  1:16 ` [PATCH 08/10] tracing: Simplify test for function_graph tracing Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 09/10] tracing: Use the hashlist for graph function Frederic Weisbecker
2010-01-25  8:50   ` Lai Jiangshan
2010-01-30 21:19     ` Frederic Weisbecker
2010-01-22  1:16 ` [RFC PATCH 10/10] ftrace: Factorize search and insertion in the function hashlist Frederic Weisbecker

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