lkml.org 
[lkml]   [2006]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Turn rdmsr, rdtsc into inline functions, clarify names
On Mon, Aug 07, 2006 at 02:56:39PM +0200, Andi Kleen wrote:
> On Mon, Aug 07, 2006 at 02:48:55PM +0200, Vojtech Pavlik wrote:
> > On Mon, Aug 07, 2006 at 02:28:45PM +0200, Andi Kleen wrote:
> > > On Mon, Aug 07, 2006 at 01:09:31PM +0200, Vojtech Pavlik wrote:
> > > > On Mon, Aug 07, 2006 at 10:48:50AM +0200, Andi Kleen wrote:
> > > > > On Sun, Aug 06, 2006 at 10:43:44PM -0400, Dmitry Torokhov wrote:
> > > > > > On Saturday 05 August 2006 23:16, Andi Kleen wrote:
> > > > > > > This whole thing is broken, e.g. on a preemptive kernel when the
> > > > > > > code can switch CPUs
> > > > > > >
> > > > > >
> > > > > > Would not preempt_disable fix that?
> > > > >
> > > > > Partially, but you still have other problems. Please just get rid
> > > > > of it. Why do we have timer code in the kernel if you then chose
> > > > > not to use it?
> > > >
> > > > The problem is that gettimeofday() is not always fast.
> > >
> > > When it is not fast that means it is not reliable and then you're
> > > also not well off using it anyways.
> >
> > I assume you wanted to say "When gettimeofday() is slow, it means TSC is
> > not reliable", which I agree with.
> >
> > But I need, in the driver, in the no-TSC case use i/o counting, not a
> > slow but reliable method. And I can't say, from outside the timing
> > subsystem, whether gettimeofday() is fast or slow.
>
> Hmm if that is the only obstacle I can export a "slow gettimeofday" flag.

That would help.

> However it would be some work to implement it for all architectures.
>
> > I assume we could make it work with the monotonic timer instead.
>
> The monotonic timer is the right thing to use to make you independent
> of ntpd, but it's normally not faster or slower than gettimeofday.

Yup.

--
Vojtech Pavlik
Director SuSE Labs
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-08-07 15:21    [W:3.209 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site