I recheck the fact you found and here's what I thought: yes, the tick will be attributed to softirq, however as we know disabling local bottom halves won't happen too long...so soon after it's enabled again, tick accounting will be back attributed to system time.
I hacked the kernel so that account_system_time() can differentiate between "true" soft IRQs and code running under local_bh_disable(). (The hack itself is quite ugly, but does the job). An experiment that sends UDP packets as quickly as possible, now shows that over 25% of the time is taken by the latter. Here's a snapshot of the /proc/stat values, normalised and displayed as percentage of the total time (similar to mpstat): CPU %user %nice %sys %iowait %irq %soft %steal %guest %bh_dis %idle 0 2.01 0.00 46.73 0.00 3.02 23.62 0.00 0.00 24.62 0.00 0 2.49 0.00 44.28 0.00 2.99 21.89 0.00 0.00 28.36 0.00 0 1.52 0.00 44.95 0.00 3.03 22.22 0.00 0.00 28.28 0.00 0 1.49 0.00 48.51 0.00 2.97 21.29 0.00 0.00 25.74 0.00 0 3.50 0.00 48.50 0.00 3.50 23.50 0.00 0.00 21.00 0.00 0 2.51 0.00 44.72 0.00 3.02 23.12 0.00 0.00 26.63 0.00 0 3.98 0.00 47.76 0.00 2.49 23.38 0.00 0.00 22.39 0.00 0 2.00 0.00 45.00 0.00 2.50 24.00 0.00 0.00 26.50 0.00 0 1.51 0.00 49.25 0.00 2.51 23.62 0.00 0.00 23.12 0.00 The bh_dis field is the one I added. Clearly, this is not a negligible amount of processor time. Elad -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
