linux-kernel - Re: [RFC patch 2/5] hrtimer: Make use of the active bases bitfield

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Message-ID: <20140225120149.GR9987@twins.programming.kicks-ass.net>
Date:	Tue, 25 Feb 2014 13:01:49 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Anton Vorontsov <anton@...msg.org>,
	Alexey Perevalov <a.perevalov@...sung.com>,
	kyungmin.park@...sung.com, cw00.choi@...sung.com
Subject: Re: [RFC patch 2/5] hrtimer: Make use of the active bases bitfield

On Fri, Feb 21, 2014 at 05:56:16PM -0000, Thomas Gleixner wrote:
> -	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
> +	while (bases) {
>  		struct hrtimer_clock_base *base;
>  		struct timerqueue_node *node;
>  		ktime_t basenow;
> +		int idx;
>  
> -		if (!(cpu_base->active_bases & (1 << i)))
> -			continue;
> +		idx = __ffs(bases);
> +		bases &= ~(1 << idx);
>  
> -		base = cpu_base->clock_base + i;
> +		base = cpu_base->clock_base + idx;
>  		basenow = ktime_add(now, base->offset);
>  
>  		while ((node = timerqueue_getnext(&base->active))) {

That's crappy for archs that end up using the generic __ffs().

The simply loop we had isn't too bad, why change this?
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