I'm running a server recently installed with centos 4.2. It's running the kernel in the subject line, on an PIII 866Mhz with 512mb ram. The system is running basically two processes: 1) ssh to remote system, receiving a stream of bytes piped into 2) gzip the stream, write to disk file The system is slow, relatively (866Mhz cpu) and the network is fast (gigabit) so the limiting factor should be CPU. And it is. However, at times, the system gets into a 'weird' state where instead of using about 85% user/ 15% system, it goes to 50% user and 50% system. Now 50% system time for this load is ridiculous, and as I said before, most of the time it is 85/15 and only occasionally get's 'stuck' in 50/50. So I got oprofile running to find out what part of the kernel it is stuck in, and here is the output of opreport -l vmlinux (top scores only): CPU: CPU with timer interrupt, speed 0 MHz (estimated) Profiling through timer interrupt samples % symbol name 21117 36.5340 default_idle 3850 6.6608 __copy_from_user_ll 3108 5.3771 find_get_page 1707 2.9532 __copy_user_intel 1580 2.7335 __might_sleep 1356 2.3460 handle_IRQ_event 1323 2.2889 __copy_to_user_ll 1168 2.0207 __find_get_block_slow 1134 1.9619 __find_get_block 1093 1.8910 finish_task_switch 963 1.6661 bh_lru_install 638 1.1038 __wake_up 605 1.0467 __do_softirq This is CRAZY! How can default_idle be sucking away cycles when the system is (should be) cpubound? Can anyone explain this? David