A useful document for explaining interrupt throttling triggered by high network load
I was tuning network performance under high traffic load on FreeBSD and stumbled across some parameters on the em drivers for the Intel Gigabit Network Card. The man page of em(4) explains briefly whatrx_int_delay, tx_int_delay, rx_abs_int_delay and tx_abs_int_delay refers to. However, I need to have a better understanding of how they actually work. After googling, I found this document by Intel which gives a really thorough jargons free description with lot of good diagrams.
I tweaked the parameters and it does give a better throughput under high network load, suppresses interrupt throttling which frees extra CPU cycle on other tasks.