Messages in this thread | | | From | "Chen, Kenneth W" <> | Subject | RE: Regression seen for patch "sched:dont decrease idle sleep avg" | Date | Thu, 18 May 2006 16:34:39 -0700 |
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Con Kolivas wrote on Wednesday, May 17, 2006 10:52 PM > The relationship between INTERACTIVE_SLEEP and the ceiling is not perfect > and not explicit enough. The sleep boost is not supposed to be any larger > than without this code and the comment is not clear enough about what exactly > it does, just the reason it does it. > > There is a ceiling to the priority beyond which tasks that only ever sleep > for very long periods cannot surpass. > > Opportunity to micro-optimise and re-use the ceiling variable. > > --- linux-2.6.17-rc4-mm1.orig/kernel/sched.c 2006-05-17 15:57:49.000000000 +1000 > +++ linux-2.6.17-rc4-mm1/kernel/sched.c 2006-05-18 15:48:47.000000000 +1000 > @@ -925,12 +924,12 @@ static int recalc_task_prio(task_t *p, u > * are likely to be waiting on I/O > */ > if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) { > - if (p->sleep_avg >= INTERACTIVE_SLEEP(p)) > + if (p->sleep_avg >= ceiling) > sleep_time = 0; > else if (p->sleep_avg + sleep_time >= > - INTERACTIVE_SLEEP(p)) { > - p->sleep_avg = INTERACTIVE_SLEEP(p); > - sleep_time = 0; > + ceiling) { > + p->sleep_avg = ceiling; > + sleep_time = 0;
Watch for white space damage, last two lines has one extra tab on the indentation.
By the way, there is all kinds of non-linear behavior with priority boost adjustment:
if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) { if (p->sleep_avg >= ceiling) sleep_time = 0; else if (p->sleep_avg + sleep_time >= ceiling) { p->sleep_avg = ceiling; sleep_time = 0; } }
For large p->sleep_avg, kernel don't clamp it to ceiling, yet clamp small incremental sleep. This all seems very fragile.
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