linux-kernel - Re: [PATCH 3/4] perf_counter: frequency based adaptive irq

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Date:	Fri, 15 May 2009 15:35:47 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 3/4] perf_counter: frequency based adaptive irq_period


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> @@ -2907,6 +2940,12 @@ perf_counter_alloc(struct perf_counter_h
>  
>  	pmu = NULL;
>  
> +	hwc = &counter->hw;
> +	if (hw_event->freq && hw_event->irq_freq)
> +		hwc->irq_period = TICK_NSEC / hw_event->irq_freq;

this needs to use a 64-bit do_div method too, otherwise we get this 
on 32-bit:

 kernel/built-in.o: In function `perf_counter_alloc':
 perf_counter.c:(.text+0x7ddc7): undefined reference to `__udivdi3'

	Ingo
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