Hi Mike, > I puttered around with your testcase a bit, and didn't see interactive > tasks starving other interactive tasks so much as plain old interactive > tasks starving expired tasks, which they're supposed to be able to do,
I inserted a trace code observing all context switches into the kernel and confirmed that less than 10 processes having max prio certainly run continuously and the others (having max - 1 prio) can run only at the beggining of the program or when runqueue are expired (the chance is about once a 200 secs in the 200 [procs/CPU] case, and their CPU time is deprived in only 1 ticks) on each CPUs. > Interactivity still seems to be fine with reasonable non-interactive > loads despite ~reserving more bandwidth for non-interactive tasks. Only > lightly tested, YMMV, and of course the standard guarantee applies ;) I've only seen your patch briefly and cant' make accurate comment yet. For the time time being, however, I examined the test which is same as my initial mail. Test environment ================ - kernel: 2.6.21-rc5 with or without Mike's patch - others: same as my initial mail except for omitting nice 19 cases Result (without Mike's patch) ============================= +---------+-----------+------+------+------+--------+ | # of | # of | avg | max | min | stdev | | CPUs | processes | (*1) | (*2) | (*3) | (*4) | +---------+-----------+------+------+------+--------+ | 1(i386) | 200 | 162 | 8258 | 1 | 1113 | +---------+-----------+------+------+------+--------+ | | | 378 | 9314 | 2 | 1421 | | 2(ia64) | 400 +------+------+------+--------+ | | | 189 |12544 | 1 | 1443 | +---------+-----------+------+------+------+--------+ *1) average number of loops among all processes *2) maximum number of loops among all processes *3) minimum number of loops among all processes *4) standard deviation Result (with Mike's patch) ========================== +---------+-----------+------+------+------+--------+ | # of | # of | avg | max | min | stdev | | CPUs | processes | | | | | +---------+-----------+------+------+------+--------+ | 1(i386) | 200 | 154 | 1114 | 1 | 210 | +---------+-----------+------+------+------+--------+ | | | 373 | 1328 | 108 | 246 | | 2(ia64) | 400 +------+------+------+--------+ | | | 186 | 1169 | 1 | 211 | +---------+-----------+------+------+------+--------+ I also gatherd tha data, changing # of processors for the 1 CPU(i386): +---------+-----------+------+------+------+--------+ | # of | # of | avg | max | min | stdev | | CPUs | processes | | | | | +---------+-----------+------+------+------+--------+ | | 25 | 1208 | 1787 | 987 | 237 | | +-----------+------+------+------+--------+ | | 50 | 868 | 1631 | 559 | 275 | | 1(i386) +-----------+------+------+------+--------+ | | 100 | 319 | 1017 | 25 | 232 | | +-----------+------+------+------+--------+ | | 200(*1) | 154 | 1114 | 1 | 210 | +---------+-----------+------+------+------+--------+ *1) Same as the above table, just for easily comparison It seems to highly depend on # of processes and at present, Ingo's patch looks better. Thanks, Satoru - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
