Priority scheduling in 6.x

Daniel Eischen deischen at
Thu Jan 15 14:38:47 PST 2009

On Thu, 15 Jan 2009, Pramod Srinivasan wrote:

> Hi Daniel
> Thanks for your response.
> On 1/14/09 7:25 PM, "Daniel Eischen" <deischen at> wrote:
>> On Wed, 14 Jan 2009, Pramod Srinivasan wrote:
>>> Hi,
>>> I have 3 threads low, medium and high , and the scheduling policy is set to
>>> SCHED_FIFO. The priority of the threads are at 28,29,30 respectively. Looks
>>> like on FreeBSD 6.x, the priority of the threads are not honored while
>>> scheduling the threads, but the same test on FreeBSD 7.x seems to work fine.
>>> Are there known issues with the priority scheduling in FreeBSD 6.x or am I
>>> doing something wrong? (I am using libthr)
>> Are you using libpthread or libthr on 6.3?
> I am using libthr on 6.1, but had similar issues on 6.2 as well.
>> If you are using libthr, then you need to be running with
>> superuser privileges for SCHED_FIFO to work.  I'm not sure
>> if this works correctly at all in 6.3.
> I am running the program with super user privileges on 6.1, tried this on
> 6.2 as well. Priority scheduling using libthr does not work, unless I am
> missing something very basic?. The same program works fine on 7.1, any
> ideas?

I'm not sure what kernel scheduler you are using (ULE or BSD),
but you can try switching it.  Other than that, it probably
just won't ever work correctly on 6.x.


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