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From: Steven Rostedt <rostedt@goodmis.org>
To: Stanislav Meduna <stano@meduna.org>
Cc: "linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: timerfd read does not return - was probably fixed in 3.4.38
Date: Thu, 02 May 2013 16:02:31 -0400	[thread overview]
Message-ID: <1367524951.7373.7.camel@gandalf.local.home> (raw)
In-Reply-To: <517B8D91.4010700@meduna.org>

On Sat, 2013-04-27 at 10:34 +0200, Stanislav Meduna wrote:

> A general question: I am seeing a few recent changes in the tracing
> code. Is it generally safe to have at least latency histogram enabled
> in the production code, or is it advised not to compile these features
> in? I'd like to see the latencies the customer is getting in the real
> environment, but if the code is considered as work-in-progress,
> it is better to play it safe.

Only the wakeup latency tracer does not cause a hit to performance. I
recommend irqsoff/preemptoff to not be enabled on production systems.
Not for safety reasons, but because they cause a noticeable overhead to
the kernel when configured in but not enabled.

As for the other tracers, the function tracer is usually fine. But some
have said that they see a slight performance decrease when configured
in. I haven't seen that, but it really does depend on the hardware.

The events should not be an issue to configure in.

-- Steve



  parent reply	other threads:[~2013-05-02 20:02 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-15 11:02 hrtimer: interrupt took 6742 ns, then RT throttling and hung machine for nearly 2 seconds Stanislav Meduna
2013-04-15 11:54 ` Stanislav Meduna
2013-04-15 12:22 ` Thomas Gleixner
2013-04-15 12:56   ` Stanislav Meduna
2013-04-17 15:46     ` timerfd and softirqd [Was: Re: hrtimer: interrupt took 6742 ns, then RT throttling and hung machine for nearly 2 seconds] Stanislav Meduna
2013-04-18  9:11       ` timerfd read does not return [Was: Re: timerfd and softirqd] Stanislav Meduna
2013-04-19 19:53         ` Stanislav Meduna
2013-04-22  7:35           ` [PATCH] Re: timerfd read does not return Stanislav Meduna
2013-04-22  8:55             ` Stanislav Meduna
2013-04-27  8:34         ` timerfd read does not return - was probably fixed in 3.4.38 Stanislav Meduna
2013-04-28 11:53           ` Carsten Emde
2013-04-29  8:43             ` Stanislav Meduna
2013-05-02 20:02           ` Steven Rostedt [this message]
2013-05-10 12:42           ` timerfd read does not return - some traces Stanislav Meduna
2013-05-12 17:31             ` Stanislav Meduna
2013-05-12 23:20             ` timerfd read does not return - hangs inside put_user Stanislav Meduna
2013-05-13  8:05               ` timerfd read does not return - caused by MM fault Stanislav Meduna
2013-05-14  8:31                 ` Livelock in handle_pte_fault [Was: Re: timerfd read does not return] Stanislav Meduna
2013-11-25 10:36                   ` Vijay Katoch

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