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Subject: Re: [PATCH] Use uname not sysctl to get the kernel revision
From: Arjan van de Ven <arjan@infradead.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Jakub Jelinek <jakub@redhat.com>,
       Ulrich Drepper <drepper@redhat.com>, Roland McGrath <roland@redhat.com>,
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Date: Wed, 12 Jul 2006 23:29:26 +0200
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On Wed, 2006-07-12 at 15:23 -0600, Eric W. Biederman wrote:
> "H. Peter Anvin" <hpa@zytor.com> writes:
> 
> > Jakub Jelinek wrote:
> >> On Wed, Jul 12, 2006 at 12:33:56PM -0700, Ulrich Drepper wrote:
> >>> Roland McGrath wrote:
> >>>> We could also put the uname info (modulo nodename) into the vDSO.
> >>> Or even better: real topology information.
> >> AND rather than OR would be even better.  So glibc could find kernel
> >> version, etc. and topology in the vDSO cheaply.
> >
> > Wouldn't it make more sense for this to be in ELF tags, rather than the vdso?
> > Another alternative, I guess, would be to put a pointer in the ELF tags, which
> > may point into the vdso.
> 
> Cheap and simple access to topology information would be interesting.
> 
> Glibc just wants to know if our kernel is SMP so it can know if it is
> ok to busy wait for a bit waiting for a mutex.  Or if busy waiting is
> a complete loss.


with current power management... busy waiting pretty much is a loss even
on UP