Messages in this thread Patch in this message | | | Date | Mon, 7 Jan 2002 08:22:44 +0100 (CET) | From | Matthias Hanisch <> | Subject | Re: 2.5.2-pre performance degradation on an old 486 |
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On Sat, 5 Jan 2002, Davide Libenzi wrote:
> There should be some part of the kernel that assume a certain scheduler > behavior. There was a guy that reported a bad hdparm performance and i > tried it. By running hdparm -t my system has a context switch of 20-30 > and an irq load of about 100-110.
This guy was me, IMHO (just with my office email address :).
> The scheduler itself, even if you code it in visual basic, cannot make > this with such loads. > Did you try to profile the kernel ?
To answer your question, I wanted to profile 2.5.2-pre8 against 2.5.2-pre8-old-scheduler. _Fortunately_ I made some mistake and forgot to back out the following chunk of memory.
--- v2.5.1/linux/arch/i386/kernel/process.c Thu Oct 4 18:42:54 2001 +++ linux/arch/i386/kernel/process.c Thu Dec 27 08:21:28 2001 @@ -125,7 +125,6 @@ /* endless idle loop with no priority at all */ init_idle(); current->nice = 20; - current->counter = -100; while (1) { void (*idle)(void) = pm_idle; So it seems, that removing this line from kernel sources with the old scheduler causes this unresponsive behavior. This chunk looks also a little bit strange. In most (all?) the other chunks "counter" gots replaced with "dyn_prio", not completely removed.
I'll verify this tonight (have to earn some money at first :). I'll do also some profiling.
Mikael, if you have time, maybe you can try to apply only this chunk of patch (or only remove the line) to a clean 2.4.18-pre1 and report the behavior.
Davide, regarding your question in the other mail:
> Can you try some changes that i'll tell you ?
Please forward to me also. Sometimes it takes a little bit longer, because there is also life without LKML, but I want to get this understood and fixed, so I'll try to help you as much as I can.
Regards, Matze
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