You generally want the following in trading:

* mean/med/p99/p999/p9999/max over day, minute, second, 10ms

* software timestamps of rdtsc counter for interval measurements - am17 says why below

* all of that not just on a timer - but also for each event - order triggered for send, cancel sent, etc - for ease of correlation to markouts.

* hw timestamps off some sort of port replicator that has under 3ns jitter - and a way to correlate to above.

* network card timestamps for similar - solar flare card (amd now) support start of frame to start of Ethernet frame measurements.