linux-kernel - Re: [PATCH 8/9] hrtimer: Allow hrtimer::function() to free the timer

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Message-ID: <alpine.DEB.2.11.1506031917030.31424@nanos>
Date:	Wed, 3 Jun 2015 19:41:43 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	umgwanakikbuti@...il.com, mingo@...e.hu, ktkhai@...allels.com,
	rostedt@...dmis.org, juri.lelli@...il.com, pang.xunlei@...aro.org,
	oleg@...hat.com, wanpeng.li@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/9] hrtimer: Allow hrtimer::function() to free the
 timer

On Wed, 3 Jun 2015, Peter Zijlstra wrote:
>  /**
>   * struct hrtimer - the basic hrtimer structure
> @@ -153,6 +144,7 @@ struct hrtimer_clock_base {
>  	struct timerqueue_head	active;
>  	ktime_t			(*get_time)(void);
>  	ktime_t			offset;
> +	struct hrtimer		*running;

Aside of lacking a KernelDoc comment, it expands the struct size on
32bit from 32 bytes to 36 bytes which undoes some of the recent cache
line optimizations I did. Mooo!

So we might think about storing the running timer pointer in cpu_base
instead for 32bit, which increases the foot print of the migration
base and the extra cost for the additional indirection, but it would
keep cache line tight for the hot pathes.

Other than that, this looks pretty good.

Thanks,

	tglx

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