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    SubjectRe: [PATCH] 2.5.72 O(1) interactivity bugfix
    Date
    On Thu, 19 Jun 2003 08:59, Andreas Boman wrote:
    > On Wed, 2003-06-18 at 18:43, Con Kolivas wrote:
    > > On Thu, 19 Jun 2003 03:59, Andreas Boman wrote:
    > > > On Wed, 2003-06-18 at 10:43, Con Kolivas wrote:
    > > > > --BEGIN PGP SIGNED MESSAGE--
    > > > > Hash: SHA1
    > > > >
    > > > > Hi Ingo, all
    > > > >
    > > > > While messing with the interactivity code I found what appears to be
    > > > > an uninitialised variable (p->sleep_avg), which is responsible for
    > > > > all the boost/penalty in the scheduler. Initialising this variable to
    > > > > 0 seems to have made absolutely massive improvements to system
    > > > > responsiveness under load and completely removed audio skips up to
    > > > > doing a make -j64 on my uniprocessor P4 (beyond which swap starts
    > > > > being used), without changing the scheduler timeslices. This seems to
    > > > > help all 2.4 O(1) based kernels as well. Attached is a patch against
    > > > > 2.5.72 but I'm not sure about the best place to initialise it.
    > > >
    > > > Applying this ontop of 2.5.72-mm1 causes more xmms/mpg321/ogg123
    > > > skipping than with plain -mm1 here. make -j20 on my up athlon 1900+
    > > > with 512M ram causes extreme skipping until the make is killed. With
    > > > plain -mm1 I may get _one_ skip at the very begining of a song during
    > > > make -j20 (about 50% of the time). Plain -mm1 stops skipping after
    > > > 10-15 sec of playback of a song, and even switching desktops after that
    > > > doesnt cause skips, with or without make -j20 running (switching
    > > > to/from desktops with apps like mozilla, evolution etc. will cause
    > > > skips during the first 10-15 sec of a song regardless what I do it
    > > > seems).
    > > >
    > > > Renicing xmms to -15 doesnt change anything with either kernel.
    > >
    > > Hmm. I got too excited with the fact it improved so much on the 2.4 O(1)
    >
    > Well, I got very exited when I saw your post ;) I guess this is a
    > problem all us UP desktop users would like too see solved.
    >
    > > kernels that I didn't try it hard enough on the 2.5 kernels. I have had
    > > people quietly telling me that it isn't uninitialised, but that I am
    > > simply resetting it with this patch on new forked processes. It seems the
    > > extra changes to the 2.5 scheduler make this patch make things worse?
    >
    > Yeah, I poked around a bit after I sent my earlier mail to see what may
    > be going on and noticed that too. (In activate_task() and sched_exit()
    > and some other place iirc)
    >
    > > I need more testing of the 2.4 one as well to see if it was just my
    > > combination of hardware and kernel that was better with this...
    >
    > I suspect that is the case, yes, or I got unlucky with mine since it was
    > extremely bad during the make -j. I'll see if I can get a 2.4.21-ck
    > patched up with some other things I need here, and try to reproduce my
    > results. That should tell us if it is infact scheduler differences or
    > our different setups.

    I had another look at 2.5 and noticed the max sleep avg is set to 10 seconds
    instead of 2 seconds in 2.4. This could make a _big_ difference to new forked
    tasks if they all start out penalised as most non-interactive. It can take 5
    times longer before they get the balance right. Can you try with this set to
    2 or even 1 second on 2.5?

    Con

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