Re: 2.6.15-rc5-mm2 :-)

Peter Williams
2005-12-13T23:30:52Z

Con Kolivas wrote:
> On Tuesday 13 December 2005 22:13, Maciej Soltysiak wrote:
>
>>Hello Con,
>>
>>Tuesday, December 13, 2005, 6:52:09 AM, you wrote:
>>
>>>I missed this announcement (been on leave for a while). This SCHED_BATCH
>>>implementation is by Ingo and it it is not "idle" scheduling as I have
>>>implemented in the staircase scheduler. This is just to restrict a task
>>>to not having any interactive bonus at any stage and to have predictable
>>>scheduling behaviour I guess.
>>
>>Thanks a lot. That's good anyway.
>>
>>If I understand correctly, if Ingo's version gets merged with linus' tree
>>your implementions of SCHED_BATCH in -ck will be replacing the one from
>>Ingo.
>
>
> Yes. SCHED_BATCH in Ingo's implementation is more like turning off the
> interactive setting in staircase, and the idle scheduling staircase offers is
> extremely useful.
>
>
>>A silly question. Is SCHED_BATCH-kind-of-thing a standard in Unices or
>>general operating system engineering know-how? Or is this concept only
>>available for Linux?
>
>
> Fairly standard in Unices but prone to all sorts of priority inversion
> starvation scenarios so very few implement it. In freebsd for example you can
> use their idle scheduling only if you are root to prevent this starvation -
> which kind of makes it useless in practice. My implementation is fairly
> robust at avoiding the priority inversion problem - at least I haven't seen a
> bug report about it for years since I address it :)
>

FYI, the 6.1.6 version of PlugSched for 2.6.15-rc5-mm2 that I announced
yesterday applies the same SCHED_BATCH semantics as Ingo's patch to the
ingosched, nicksched, zaphod and spa_ws schedulers (i.e. it suppresses
interactive bonuses for tasks in the SCHED_BATCH policy class). As
spa_no_frills and spa_svr do not have interactive bonuses there is no
change to their semantics. The staircase scheduler in PlugSched will be
updated to the same SCHED_BATCH as the stand alone version in due course.

Peter
--
Peter Williams pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce