Re: Ten percent test

Gene Heskett
2007-04-08T11:33:43Z

On Sunday 08 April 2007, Ingo Molnar wrote:
>* Gene Heskett <gene.heskett@gmail.com> wrote:
>> That said, I am booted to the patch you sent me now, and this also is
>> a very obvious improvement, one I could easily live with on a long
>> term basis. I haven't tried a kernel build in the background yet, but
>> I have sat here and played patience for about an hour, looking for the
>> little stutters, but never saw them. So I could just as easily
>> recommend this one for desktop use, it seems to be working. tvtime
>> hasn't had any audio or video glitches that I've noted when I was on
>> that screen to check on an interesting story, like the 102 year old
>> lady who finally got her hole in one, on a very short hole, but after
>> 90 years of golfing, she was beginning to wonder if she would ever get
>> one. Not sure who bought at the 19th hole, HNN didn't cover that
>> traditional part.
>>
>> So this patch also works. And if it gets into mainline, at least
>> Con's efforts at proding the fixes needed will not have been in vain.
>
>thanks for testing it! (for the record, Gene tested sched-mike-4.patch,
>which is Mike's patch from 4 days ago.)
>
>> My question then, is why did it take a very public cat-fight to get
>> this looked at and the code adjusted? Its been what, nearly 2 years
>> since Linus himself made a comment that this thing needed fixed. The
>> fixes then done were of very little actual effectiveness and the
>> situation then has gradually deteriorated since.
>
>this is pretty hard to get right, and the most objective way to change
>it is to do it testcase-driven. FYI, interactivity tweaking has been
>gradual, the last bigger round of interactivity changes were done a year
>ago:
>
> commit 5ce74abe788a26698876e66b9c9ce7e7acc25413
> Author: Mike Galbraith <efault@gmx.de>
> Date: Mon Apr 10 22:52:44 2006 -0700
>
> [PATCH] sched: fix interactive task starvation
>
>(and a few smaller tweaks since then too.)
>
>and that change from Mike responded to a testcase. Mike's latest changes
>(the ones you just tested) were mostly driven by actual testcases too,
>which measured long-term timeslice distribution fairness.
>
>It's really hard to judge interactivity subjectively, so we rely on
>things like interbench (written by Con) - in which testsuite the
>upstream scheduler didnt fare all that badly, plus other testcases
>(thud.c, game_sim.c, now massive_inter.c, fiftyp.c and chew.c) and all
>the usual test-workloads. This is admittedly a slow process, but it
>seems to be working too and it also ensures that we dont regress in the
>future. (because testcases stick around and do get re-tested)
>
>your system seems to also be a bit special because you 1) drive it to
>the absolute max on the desktop but you do not overload it in obvious
>ways (i.e. your workloads are pretty fairly structured) 2) it's a bit
>under-powered (single-CPU 800 MHz CPU, right?) but not _too_
>underpowered - so i think you /just/ managed to hit 'the worst' of the
>current interactivity estimator: with important tasks both being just
>above and just below 50%. Believe me, on all ~10 systems i use
>regularly, Linux interactivity of the vanilla scheduler is stellar. (And
>that includes a really old 500 MHz one too with FC6 on it.)

Actually, its an XP2800 Athlon, 333 fsb, gig of memory. And I was all
enthusiastic about this until amanda's nightly run started, at which
point I started losing control for quite long periods, 30+ seconds at a
time. Up till then I thought we had it made. In this regard, Cons
patches were enough better to notice it right away, lags were 1-2 seconds
max.

That seems to be the killer loading here, building a kernel (make -j3)
doesn't seem to lag it all that bad. One session of gzip -best makes it
fall plumb over though, which was a disappointment.

But, I could live with this.

Now if I could figure out a way to nail dm_mod down to a fixed LANANA
approved address, I just got bit again, because enabling pktcdvd caused a
MAJOR switch, only from 253 to 252 but tar thinks the whole 45GB is all
new again. So since it, dm_mod, no longer carries the experimental
label, lets put that patch back in and be done with this particular
hassle once and for all. If I had known that using LVM2 was going to be
such a pain in the ass just with this item alone, I wouldn't have touched
it with a 50 foot fiberglass pole. Or does this SOB effect normal
partition mountings too? I don't know, and the suggested fixes from
David Dillow I put in /etc/modprobe.conf are ignored for dm_mod, and when
extended to pktcdvd, cause pktcdvd to fail totally.

Mmm??, can I pass an 'option dm_mod major=238' as a kernel argument & make
it work that way? This is extremely frustrating as it is now.

> Ingo

--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Real Programmers don't write in PL/I. PL/I is for programmers who can't
decide whether to write in COBOL or FORTRAN.