microsecond event scheduling in an application

microsecond event scheduling in an application

[Junhee Lee]

I am working on event scheduler which handles events in microsecond level.
Actual this program is a network emulator using simulation codes.
I'd like to expect that network emulator is working as simulation behaviors.
Thus high resolution timer interrupt is required.
But high resolution timer interrupt derived by high tick frequency (jiffies
clock) must effect the system performance. 
Are there any comments or ways to support microsecond event scheduling
without performance degradation?

Regards 

Re: microsecond event scheduling in an application

[Robert Hancock]

On 09/08/2009 08:27 AM, Junhee Lee wrote:
> I am working on event scheduler which handles events in microsecond level.
> Actual this program is a network emulator using simulation codes.
> I'd like to expect that network emulator is working as simulation behaviors.
> Thus high resolution timer interrupt is required.
> But high resolution timer interrupt derived by high tick frequency (jiffies
> clock) must effect the system performance.
> Are there any comments or ways to support microsecond event scheduling
> without performance degradation?

Just increasing HZ will degrade performance, yes, but we have hrtimers 
now which should be able to use granularities smaller than one jiffy, so 
it shouldn't be needed..

Re: microsecond event scheduling in an application

[Arjan van de Ven]

On Sun, 20 Sep 2009 12:26:09 -0600
Robert Hancock <hancockrwd@gmail.com> wrote:

> On 09/08/2009 08:27 AM, Junhee Lee wrote:
> > I am working on event scheduler which handles events in microsecond
> > level. Actual this program is a network emulator using simulation
> > codes. I'd like to expect that network emulator is working as
> > simulation behaviors. Thus high resolution timer interrupt is
> > required. But high resolution timer interrupt derived by high tick
> > frequency (jiffies clock) must effect the system performance.
> > Are there any comments or ways to support microsecond event
> > scheduling without performance degradation?
> 
> Just increasing HZ will degrade performance, yes, but we have
> hrtimers now which should be able to use granularities smaller than
> one jiffy, so it shouldn't be needed..


select/poll use hrtimers, which are jiffies independent....

you'll be hard pressed to notice jiffies granularity in userspace
nowadays..



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

RE: microsecond event scheduling in an application

[Junhee Lee]

Thanks Arjan van de Ven. 
Your comment is very useful to me.
Now I am trying to solve microsecond events scheduling using hrtimer.

-----Original Message-----
From: Arjan van de Ven [mailto:arjan@infradead.org] 
Sent: Monday, September 21, 2009 3:31 AM
To: Robert Hancock
Cc: Junhee Lee; linux-kernel@vger.kernel.org
Subject: Re: microsecond event scheduling in an application

On Sun, 20 Sep 2009 12:26:09 -0600
Robert Hancock <hancockrwd@gmail.com> wrote:

> On 09/08/2009 08:27 AM, Junhee Lee wrote:
> > I am working on event scheduler which handles events in microsecond
> > level. Actual this program is a network emulator using simulation
> > codes. I'd like to expect that network emulator is working as
> > simulation behaviors. Thus high resolution timer interrupt is
> > required. But high resolution timer interrupt derived by high tick
> > frequency (jiffies clock) must effect the system performance.
> > Are there any comments or ways to support microsecond event
> > scheduling without performance degradation?
> 
> Just increasing HZ will degrade performance, yes, but we have
> hrtimers now which should be able to use granularities smaller than
> one jiffy, so it shouldn't be needed..


select/poll use hrtimers, which are jiffies independent....

you'll be hard pressed to notice jiffies granularity in userspace
nowadays..



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org