Hi, On Wed, 1 Aug 2007, Ingo Molnar wrote:
> > [...] e.g. in this example there are three tasks that run only for > > about 1ms every 3ms, but they get far more time than should have > > gotten fairly: > > > > 4544 roman 20 0 1796 520 432 S 32.1 0.4 0:21.08 lt > > 4545 roman 20 0 1796 344 256 R 32.1 0.3 0:21.07 lt > > 4546 roman 20 0 1796 344 256 R 31.7 0.3 0:21.07 lt > > 4547 roman 20 0 1532 272 216 R 3.3 0.2 0:01.94 l > > Mike and me have managed to reproduce similarly looking 'top' output, > but it takes some effort: we had to deliberately run a non-TSC > sched_clock(), CONFIG_HZ=100, !CONFIG_NO_HZ and !CONFIG_HIGH_RES_TIMERS. I used my old laptop for these tests, where tsc is indeed disabled due to instability. Otherwise the kernel was configured with CONFIG_HZ=1000. > in that case 'top' accounting symptoms similar to the above are not due > to the scheduler starvation you suspected, but due the effect of a > low-resolution scheduler clock and a tightly coupled timer/scheduler > tick to it. Well, it magnifies the rounding problems in CFS. I mainly wanted to test a little the behaviour of CFS and I thought a saw patch which enabled the use of TSC in these cases, so I didn't check sched_clock(). Anyway, I want to point out that this wasn't the main focus of what I wrote. bye, Roman - 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/