2.4.2: System clock slows down under load

2.4.2: System clock slows down under load

[Thomas Pfaff]

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Hi all,

i decided to make a test for the 2.4 kernel on my old hardware (Gigabyte
EISA/VLB with an AMD 486 DX4 133). The kernel boots fine but there is one
strange thing: The system clock slows down under load, after a make
dep in the linux src directory it is about 2 minutes behind. This appears
both in 2.4.1 and in 2.4.2 (I have not tried 2.4.0 yet).

I have attached a gzipped dmesg.

Any ideas ?

Thomas

Please CC my address as i am not a list member.

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Re: 2.4.2: System clock slows down under load

[Steven Walter]

On Tue, Mar 27, 2001 at 01:42:39PM +0200, Thomas Pfaff wrote:
> Hi all,
> 
> i decided to make a test for the 2.4 kernel on my old hardware (Gigabyte
> EISA/VLB with an AMD 486 DX4 133). The kernel boots fine but there is one
> strange thing: The system clock slows down under load, after a make
> dep in the linux src directory it is about 2 minutes behind. This appears
> both in 2.4.1 and in 2.4.2 (I have not tried 2.4.0 yet).
> 
> I have attached a gzipped dmesg.
> 
> Any ideas ?

I notice that you're using fbcon from your dmesg.  There was a
discussion about this a while back, and it was determined that fbcon
runs with interrupts disabled for unhealthily long period of time.  This
causes it to miss timer interrupts, and the system lock get behind.  See
if this slowdown occurs with vgacon.  If it does, its probably just a
cheap crystal on the motherboard.

-- 
-Steven
Freedom is the freedom to say that two plus two equals four.

Re: 2.4.2: System clock slows down under load

[Thomas Pfaff]

On Tue, 27 Mar 2001, Steven Walter wrote:

> On Tue, Mar 27, 2001 at 01:42:39PM +0200, Thomas Pfaff wrote:
> > Hi all,
> >
> > i decided to make a test for the 2.4 kernel on my old hardware (Gigabyte
> > EISA/VLB with an AMD 486 DX4 133). The kernel boots fine but there is one
> > strange thing: The system clock slows down under load, after a make
> > dep in the linux src directory it is about 2 minutes behind. This appears
> > both in 2.4.1 and in 2.4.2 (I have not tried 2.4.0 yet).
> >
> > I have attached a gzipped dmesg.
> >
> > Any ideas ?
>
> I notice that you're using fbcon from your dmesg.  There was a
> discussion about this a while back, and it was determined that fbcon
> runs with interrupts disabled for unhealthily long period of time.  This
> causes it to miss timer interrupts, and the system lock get behind.  See
> if this slowdown occurs with vgacon.  If it does, its probably just a
> cheap crystal on the motherboard.
>
> --
> -Steven
> Freedom is the freedom to say that two plus two equals four.
>
>
>

You are right. If i compile with vgacon it works fine.

I would be really glad if vesa fbcon in 2.4 would run without that problem
like in all 2.2 kernels i have installed. It is the easiest way to get X
and virtual consoles on my S3 graphic card.

Thanks,

Thomas