linux-kernel - Re: [PATCH 0/3] x86: add cpus

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Date:	Wed, 9 Apr 2008 23:21:20 +0200
From:	"Bert Wesarg" <bert.wesarg@...glemail.com>
To:	"Greg KH" <gregkh@...e.de>
Cc:	"Mike Travis" <travis@....com>, "Ingo Molnar" <mingo@...e.hu>,
	"Paul Jackson" <pj@....com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] x86: add cpus_scnprintf function v3

On Wed, Apr 9, 2008 at 11:14 PM, Greg KH <gregkh@...e.de> wrote:
>
> On Wed, Apr 09, 2008 at 10:52:58PM +0200, Bert Wesarg wrote:
>  > On Wed, Apr 9, 2008 at 10:39 PM, Greg KH <gregkh@...e.de> wrote:
>  > >
>  > > On Wed, Apr 09, 2008 at 07:51:23PM +0200, Bert Wesarg wrote:
>  > >  > On Tue, Apr 8, 2008 at 8:43 PM, Mike Travis <travis@....com> wrote:
>  > >  > >   * Cleanup usages of cpumask_scprintf in the following files and add
>  > >  > >     another interface to use cpulist_scnprintf where appropriate.
>  > >  >
>  > >  > On Mon, Apr 7, 2008 at 8:22 PM, Mike Travis <travis@....com> wrote:
>  > >  > >  Part of the change is readability, but also looking towards the future
>  > >  > >  of 16k/64k/??? # of cpus, the straight mask approach will overflow the
>  > >  > >  PAGE_SIZE buffer provided (though some pathological cases will overflow
>  > >  > >  the range method as well.)  So we'll need some advancement in the format
>  > >  > >  of the printout.
>  > >  >
>  > >  > Btw, I think you can now push for a deprecation of the 'old' mask
>  > >  > attributes, with the justification you have given above. The other
>  > >  > possibility is to change sysfs to provide bigger attribute buffers
>  > >  > (CCed Greg for this).
>  > >
>  > >  Huh?
>  > >
>  > >  sysfs is "one value per file", if you are getting close to PAGE_SIZE in
>  > >  any sysfs file, then you are doing something very wrong.
>  > >
>  > >  What sysfs file currently is trying to output data this big?
>  > Currently none. But if NR_CPUS >= 16K and PAGE_SIZE == 4K, than any
>  > file with an cpumask_scnprintf().
>
>  Do we have such sysfs files today?
Files with cpumask_scnprintf()? Sure, the cpu topology exports plenty
of cpu masks.

If you ask for files with that big NR_CPUS, than no. We are talking
only for future scenarios.

Bert
>
>  thanks,
>
>  greg k-h
>
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