linux-kernel - Re: [PATCH] tracing: Cleanup the convoluted softirq tracepoints

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Message-ID: <4CC5FC99.8090203@zytor.com>
Date:	Mon, 25 Oct 2010 14:54:33 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jason Baron <jbaron@...hat.com>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Koki Sanagi <sanagi.koki@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	nhorman@...driver.com, scott.a.mcmillan@...el.com,
	laijs@...fujitsu.com, LKML <linux-kernel@...r.kernel.org>,
	eric.dumazet@...il.com, kaneshige.kenji@...fujitsu.com,
	David Miller <davem@...emloft.net>, izumi.taku@...fujitsu.com,
	kosaki.motohiro@...fujitsu.com,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	"Luck, Tony" <tony.luck@...el.com>
Subject: Re: [PATCH] tracing: Cleanup the convoluted softirq tracepoints

On 10/20/2010 08:27 AM, Jason Baron wrote:
> 
> sure. The idea of the 'jmp 0' was simply to be an lcd for x86, if
> there's a better lcd for x86, I'll update it. But note, that since the
> 'jmp 0' is patched to a better nop at boot, we wouldn't see much gain.
> And in the boot path we are using 'text_poke_early()', so avoiding that
> isn't going to improve things much.
> 

It's still a completely unnecessary waste of startup time some
potentially significant fraction of the time.  Startup time matters,
especially as the number of tracepoints grow.

	-hpa
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