sleep and wakeup at microsecond boundary

sleep and wakeup at microsecond boundary

[NucleoDyne Systems, Inc.]

Hello,
      We have a requirement to implement the sleep and wakeup mechanism
at microsecond boundary in 2.4 kernel. The intent of this mail is to
start a discussion on this topic and collect inputs from the kernel
developers. Any reply on the issues of implementing such a feature will
be greatly appreciated.

Thanks,
Kallol Biswas

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NucleoDyne Corporation
nucleon@nucleodyne.com
www.nucleodyne.com
Phone:408-718-8164
Fax: 408-732-2284

Re: sleep and wakeup at microsecond boundary

[Arjan van de Ven]

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On Tue, 2004-09-07 at 07:46, NucleoDyne Systems, Inc. wrote:
> Hello,
>       Let me explain the requirement a little more in detail.
> 
> Consider the routine sleep_on_timeout(, timeout) in sched.c:

please don't use this routine. It's severely deprecated.

> On  x86 the jiffies is updated every time PIT raises interrupt and
> do_timer() is called, i.e. once in every 10ms.

it's 1ms nowadays....


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Re: sleep and wakeup at microsecond boundary

[NucleoDyne Systems, Inc.]

Hello,
      Let me explain the requirement a little more in detail.

Consider the routine sleep_on_timeout(, timeout) in sched.c:

A timer is started and then schedule() is called. The timer expires
after present jiffies + timeout (in jiffies) period.

On  x86 the jiffies is updated every time PIT raises interrupt and
do_timer() is called, i.e. once in every 10ms.

So we can set timeout in multiples of 10ms. 

We are developing a very powerful system (not x86 based) with multiple
CPUs, one of them will be running linux and will act as a co-processor
for the other CPUs running different OS.

On the CPU running linux we need to be able to call sleep_on_timeout()
with more granular expiration time, may be in multiples of microseconds.

I already have done the investigation and looking for feedback from the
developers on all possible issues.

Hope this explains.


Thanks,
Kallol Biswas



On Sun, 2004-09-05 at 00:09, Mike Galbraith wrote:
> At 12:51 PM 9/4/2004 -0700, NucleoDyne Systems, " "Inc. wrote:
> >Hello,
> >       We have a requirement to implement the sleep and wakeup mechanism
> >at microsecond boundary in 2.4 kernel.
> 
> I've re-visited this message about 10 times now, so I suppose I'm curious 
> enough to ask:  why on God's green Earth would someone want to do 
> that?  (to _any_ kernel, but I'm mostly wondering why [TILT] anyone would 
> do such a thing to a GP kernel)
> 
>          -Mike

On Sat, 2004-09-04 at 12:51, NucleoDyne Systems, Inc. wrote: \

> Hello,
>       We have a requirement to implement the sleep and wakeup mechanism
> at microsecond boundary in 2.4 kernel. The intent of this mail is to
> start a discussion on this topic and collect inputs from the kernel
> developers. Any reply on the issues of implementing such a feature will
> be greatly appreciated.
> 
> Thanks,
> Kallol Biswas


-- 
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NucleoDyne Corporation
nucleon@nucleodyne.com
www.nucleodyne.com
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