linux-kernel - Re: [PATCH 13/15] small_traces: Add config option to shrink trace events.

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Message-ID: <1291427770.16223.15.camel@gandalf.stny.rr.com>
Date:	Fri, 03 Dec 2010 20:56:10 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	David Sharp <dhsharp@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mrubin@...gle.com,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 13/15] small_traces: Add config option to shrink trace
 events.

[ Added Frederic on Cc ]

I rather have this as a run time option than a compile time.

You could use two different trace event structures. The normal one and a
"compact" one. Add to the "trace_options" and when it is set the traces
are compact.

-- Steve


On Fri, 2010-12-03 at 16:13 -0800, David Sharp wrote:
> This option will remove several fields from trace events to reduce the
> payload size. Under heavy load, events can be produced faster than they
> can possibly be written to disk or sent on the network. Shrinking the
> payload size will enable fitting more traces in the ring buffer, which
> therefore enables tracing for longer periods, at the cost of losing some
> relatively unimportant details.
> 
> Google-Bug-Id: 3224547
> 
> Signed-off-by: David Sharp <dhsharp@...gle.com>
> ---
>  kernel/trace/Kconfig |   12 ++++++++++++
>  1 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> index ea37e2f..9c24fe5 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -403,6 +403,18 @@ config FUNCTION_PROFILER
>  
>  	  If in doubt, say N.
>  
> +config SMALL_TRACES
> +	bool "Shrink trace events"
> +	default n
> +	help
> +	  Minimize the size of trace events. Omits fields from trace event
> +	  header like preempt_count, and lock_depth. Chooses smaller
> +	  alternative event structures. Shrinking the payload size enables
> +	  fitting more traces in the ring buffer, which enables tracing for
> +	  longer periods when the buffer can not be read as fast as it is
> +	  filled, at the cost of losing some details.
> +
> +
>  config FTRACE_MCOUNT_RECORD
>  	def_bool y
>  	depends on DYNAMIC_FTRACE


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