linux-kernel - Re: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days

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Message-ID: <alpine.DEB.2.11.1410030706220.8990@gentwo.org>
Date:	Fri, 3 Oct 2014 07:07:46 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Richard Cochran <richardcochran@...il.com>
cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: Why do we still have 32 bit counters? Interrupt counters overflow
 within 50 days

On Fri, 3 Oct 2014, Richard Cochran wrote:

> >  DECLARE_PER_CPU(char *, irq_stack_ptr);
> > -DECLARE_PER_CPU(unsigned int, irq_count);
> > +DECLARE_PER_CPU(unsigned long, irq_count);
>
> Still 32 bit on 32 bit machines...

64 bit counters on 32 bit machines are not an easy thing and could be
expensive to handle in particular because these counters are used in
performance critical hotpaths.

I thought I better leave it alone on 32 bit.

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