On Mon, 26 Nov 2007 20:36:32 -0600 (CST) [EMAIL PROTECTED] wrote: > Question: Why is ksoftirqd eating about 5 to 10 percent of my CPU on an idle > system? The problem occurs if I config the kernel with tickless > support (i.e. CONFIG_TICK_ONESHOT=y). (Thanks to "oprofile" for putting me > onto this.)
beware that oprofile can provide misleading results on a paritally-idle system. You may have discovered that ksoftirqd is consuming 5-10% of the non-idle time on that idle system, which is less surprising. > I have noted this same problem on kernel versions: 2.6.23.1, 2.6.23.8 and > 2.6.23.9 > > ************************************************************************** > *** Output from "vmstat -n 1 10" -- Note very high context switch rate *** > *** This is on a idle machine! *** > ************************************************************************** > > procs -----------memory---------- ---swap-- -----io---- --system-- > ----cpu---- > r b swpd free buff cache si so bi bo in cs us sy > id wa > 0 0 0 1925556 4768 116104 0 0 124 2 6 7538 1 2 > 96 1 > 0 0 0 1925556 4768 116104 0 0 0 0 2 147329 0 1 > 99 0 > 0 0 0 1925548 4768 116104 0 0 0 0 0 154515 0 1 > 99 0 > 0 0 0 1925548 4768 116104 0 0 0 0 1 153898 0 2 > 98 0 > 0 0 0 1925548 4780 116104 0 0 0 16 3 155216 0 1 > 99 0 > 0 0 0 1925548 4780 116104 0 0 0 0 1 161718 0 1 > 99 0 > 0 0 0 1925548 4780 116104 0 0 0 0 0 147587 0 2 > 98 0 > 0 0 0 1925548 4780 116104 0 0 0 0 1 153524 0 2 > 98 0 > 0 0 0 1925448 4780 116104 0 0 0 0 0 153434 0 1 > 99 0 > 0 0 0 1925448 4792 116092 0 0 0 16 4 153527 0 2 > 98 0 So what piece of code is scheduling so much? What does `top' say? What does the (sorted) output of oprofile look like? Did you try shutting down as much userspace code as possible to find out if some userspace task is misbehaving? - 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/
