SCHED_4BSD bad interactivity on 7.0 vs 6.3

[Garrett Cooper]

On Sun, Jul 13, 2008 at 12:47 AM, Eugene Grosbein <eugen at kuzbass.ru> wrote:
> On Sun, Jul 13, 2008 at 03:11:23AM +0200, Kris Kennaway wrote:
>
>> >It seems like there has been a regression in interactivity from
>> >6.3-RELEASE to 7.0-RELEASE when using the SCHED_4BSD scheduler.  After
>> >upgrading my single-cpu amd64 box, 7.0 has much worse latency.  When
>> >running a kernel compile, there is a noticeable lag to echo my typing or
>> >scroll my browser windows, and playing an mp3 frequently cuts out for a
>> >second or two.  This did not happen on 6.3-RELEASE.
>>
>> Are you sure it's not the x.org server bug that was present in the
>> version shipped with 7.0?
>
> No, it's not. I have exactly the same problem with SCHED_4BSD
> after upgrade from 6.3-STABLE to 7.0-STABLE. I didn't upgrade
> my x.org 6.9.0, only OS (all 6.x compat shims are installed).
> There is some sort of regression, certainly.

IIRC some folks reported performance degradation using SCHED_4BSD in
the past after the SMP fixes, so this isn't a new news story.

SCHED_ULE isn't going to be default until 7.1-RELEASE I believe
because they might be fanning out a few bugs in -CURRENT (the number
of bugs are small from what I've seen) and MFC'ing them to 7-RELEASE.

-Garrett