Messages in this thread | | | Subject | Re: patch-O1int-0306281420 for 2.5.73 interactivity | From | Roberto Orenstein <> | Date | 28 Jun 2003 19:45:01 -0300 |
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On Sat, 2003-06-28 at 17:26, pat erley wrote: > I made a small error when I sent Con a piece of magic I wrote up to help the sleep period. > > what it says right now: > > /kernel/sched.c around line 325 > > > sleep_period = (sleep_period * > 17 * sleep_period / ((17 * sleep_period / (5 * tau) + 2) * 5 * tau)); > ----------------------------------------------------------^ > > it should be: > > sleep_period = (sleep_period * > 17 * sleep_period / ((17 * sleep_period / (5 * tau + 2)) * 5 * tau)); > --------------------------------------------------------------^ > > stupid parenthesis. > > a little background. what this essentially is is a taylor approximation of the function ln(66x+1) normalized. ln(66x+1) happens to do a great job oas a weighting function on the range of 0 to 1, and because the input only happens to range from 0 to 1, only 2 terms were needed to do a 'good enough' job. > > Pat
I did your correction and I got a kernel panic(attempting to kill init) on boot. It didn't flushed to disk, so it isn't attached, but it panics at effective_prio+0xcc/0xe0. With objdump I could see it traps a division by 0: cc: f7 fb idiv %ebx
I remember cleary %ebx being 0 on the panic report. And I tracked down and the code is on this else in effective_prio: ----------- sched.c 341----------------- else { sleep_period = (sleep_period * 17 * sleep_period / ((17 * sleep_period / (5 * tau + 2)) * 5 * tau)); if (!sleep_period) return p->static_prio; } --------------------------------------
I don't have the time now to track this further today, but what happens if sleep_period is too small and tau is too big? Could this (17 * sleep_period / (5 * tau + 2) give 0 and so a division by 0?
abs Roberto
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