2003-01-02 14:35:44

by uaca

[permalink] [raw]
Subject: CONFIG_X86_TSC_DISABLE question

Hi all

I would like to know if in wich degree the issue of unsynced TSCs also applies
on x86 SMP.

Thanks

Ulisses

Debian GNU/Linux: a dream come true
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2003-01-02 17:31:24

by Martin J. Bligh

[permalink] [raw]
Subject: Re: CONFIG_X86_TSC_DISABLE question

Depends on your box. Most standard SMP boxes are all clocked off the
same clock, so it's not an issue.

--On Thursday, January 02, 2003 15:44:09 +0100 [email protected] wrote:

> Hi all
>
> I would like to know if in wich degree the issue of unsynced TSCs also
> applies on x86 SMP.
>
> Thanks
>
> Ulisses
>
> Debian GNU/Linux: a dream come true
> -------------------------------------------------------------------------
> ---- "Computers are useless. They can only give answers."
> Pablo Picasso
>
> ---> Visita http://www.valux.org/ para saber acerca de la <---
> ---> Asociaci?n Valenciana de Usuarios de Linux <---
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
>


2003-01-02 17:49:25

by uaca

[permalink] [raw]
Subject: Re: CONFIG_X86_TSC_DISABLE question

On Thu, Jan 02, 2003 at 09:39:40AM -0800, Martin J. Bligh wrote:
> Depends on your box. Most standard SMP boxes are all clocked off the
> same clock, so it's not an issue.

Hi Martin

Thanks for your reply

Is there a way to verify this? or must I contact the motherboard maker and
ask for it? how I should ask it?


Ulisses

>
> --On Thursday, January 02, 2003 15:44:09 +0100 [email protected] wrote:
>
> >Hi all
> >
> >I would like to know if in wich degree the issue of unsynced TSCs also
> >applies on x86 SMP.
> >
> >Thanks
> >
> > Ulisses
> >
> > Debian GNU/Linux: a dream come true
> >-------------------------------------------------------------------------
> >---- "Computers are useless. They can only give answers."
> >Pablo Picasso
> >
> >---> Visita http://www.valux.org/ para saber acerca de la <---
> >---> Asociaci?n Valenciana de Usuarios de Linux <---
> >
> >-
> >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> >the body of a message to [email protected]
> >More majordomo info at http://vger.kernel.org/majordomo-info.html
> >Please read the FAQ at http://www.tux.org/lkml/
> >
> >
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/

--
Debian GNU/Linux: a dream come true
-----------------------------------------------------------------------------
"Computers are useless. They can only give answers." Pablo Picasso

---> Visita http://www.valux.org/ para saber acerca de la <---
---> Asociaci?n Valenciana de Usuarios de Linux <---

2003-01-02 18:34:45

by Martin J. Bligh

[permalink] [raw]
Subject: Re: CONFIG_X86_TSC_DISABLE question

> Is there a way to verify this? or must I contact the motherboard maker and
> ask for it? how I should ask it?

I'd just assume that it works unless you have > 4 CPUs. Boxes (like mine)
where it doesn't work tend to be arcane NUMA things with large CPU counts.

M.

2003-01-03 22:49:42

by uaca

[permalink] [raw]
Subject: Re: CONFIG_X86_TSC_DISABLE question


On Fri, Jan 03, 2003 at 05:52:55PM -0500, Mark Hahn wrote:

Hi Mark

> > > Depends on your box. Most standard SMP boxes are all clocked off the
> > > same clock, so it's not an issue.
> >
> > Hi Martin
> >
> > Thanks for your reply
> >
> > Is there a way to verify this? or must I contact the motherboard maker and
> > ask for it? how I should ask it?
>
> any SMP less than $50k is using a single clock to drive the CPUs,
> and therefore has TSC's in sync. if you owned a numa/clustered
> SMP, you'd know it - they're the only ones that need something special.

Thanks for your reply

I think that CONFIG_X86_TSC_DISABLE should be more informative on this

Ulisses


Debian GNU/Linux: a dream come true
-----------------------------------------------------------------------------
"Computers are useless. They can only give answers." Pablo Picasso

---> Visita http://www.valux.org/ para saber acerca de la <---
---> Asociaci?n Valenciana de Usuarios de Linux <---

2003-01-06 16:13:46

by uaca

[permalink] [raw]
Subject: Re: CONFIG_X86_TSC_DISABLE question

On Fri, Jan 03, 2003 at 06:01:13PM -0500, Mark Hahn wrote:
> > I think that CONFIG_X86_TSC_DISABLE should be more informative on this
>
> at most, it should say "don't worry about this unless you need to.
> and you'll know it if you need to".


And It should say that the kernel test TSCs are syncroniced across CPUS at
boot time, which I've just have found:

The message is the following in a 2.4.19-pre6 kernel

checking TSC synchronization across CPUs: passed.


I hope this helps somebody


Ulisses

Debian GNU/Linux: a dream come true
-----------------------------------------------------------------------------
"Computers are useless. They can only give answers." Pablo Picasso

---> Visita http://www.valux.org/ para saber acerca de la <---
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