linux-kernel - Re: register_timer_hook use in arch/sh/oprofile

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Message-ID: <20090624121750.GB20564@elte.hu>
Date:	Wed, 24 Jun 2009 14:17:50 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Paul Mundt <lethal@...ux-sh.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: register_timer_hook use in arch/sh/oprofile


* Paul Mundt <lethal@...ux-sh.org> wrote:

> In practice oprofile has never been a good fit for these sorts of 
> counters, so this has fairly limited use. If there's a way to 
> wiggle these types of counters in to the new perf_counter API, 
> then I'll convert that over and just kill the old oprofile driver 
> off completely. Barring that, I'll just end up converting it over 
> to hrtimers as well, so don't let that stop you from ripping out 
> the timer hook bits.
> 
> Most of this code predates hrtimers anyways, and it also predates 
> the timer hook, which is only something that we converted to some 
> years back.

Note, the current initial upstream SH support for perfcounters:

 arch/sh/include/asm/perf_counter.h:#define set_perf_counter_pending()	do { } while (0)
 arch/sh/include/asm/unistd_32.h:#define __NR_perf_counter_open	336
 arch/sh/include/asm/unistd_64.h:#define __NR_perf_counter_open	364
 arch/sh/kernel/syscalls_32.S:	.long sys_perf_counter_open
 arch/sh/kernel/syscalls_64.S:	.long sys_perf_counter_open

Should already give you hrtimers straight away.

To test it, could you try to run 'perf top' after:

	cd tools/perf/
	make install

It should display a hrtimer driven kernel profile already. You can 
increase/decrease the frequency of sampling by using -F option - say 
'perf top -F 10000' should sample at 10 KHz.

Please let me know if any of this does not work as expected.

	Ingo
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