On Mon, 07 Jun 2021 11:59:20 +0200, Hannes Reinecke wrote:
On 6/3/21 11:37 AM, Thomas Hartwig wrote:
I am wondering if there is any kernel available by default which offers kernel interrupt timer (CONFIG_HZ) at 1000 Hz. I checked preempt in 15.2 but there it is 250 Hz. Why this is kept at 250 Hz there?
Primarily for historical reasons; 250 Hz was found to be a good compromise between interactive and non-interactive tasks.
My use case is very special: my environment is dealing with high speed cameras and the low frequency is needed to be able to manage high frame speed at several thousand frames per second. Right now I am using a special desktop kernel from a foreign source however I am wondering if there is any chance to have this into mainline LEAP distro available? I know my use case is very special and I should be able to maintain my own kernel for this, however I am wondering if this would be a nice benefit of the LEAP distribution in general and why the preempt kernel is kept at lower frequency still...
Actually this sounds like a case for the realtime kernel. If you have hardware with specific timing needs I would have thought that the driver/application/what have you should be moved to employing a 'realtime' scheduling policy, and manage the frame capture from within the driver rather than relying on the kernel interrupt timer to do it for you.
If you had a need for raising the interrupt timer it really sounds like a bad driver design to me ...
If, OTOH, you can convert your application to leveraging realtime priority you can look a the -rt kernel, which is geared up for precisely such usecases.
Well, if HZ=1000 really helps, it implies that it's no requirement of the hard RT, and kernel-preempt flavor would work enough for that purpose. AFAIK, kernel-preempt is available for Leap. And for TW, we're going to switch to the dynamic preempt, i.e. the preemption model is chosen via boot option. Takashi