Elad Lahav <[EMAIL PROTECTED]> asjed | I'm looking into the performance of a simple, single-threaded, TCP server on a T1000. | According to mpstat, the strand running the server is about 50% idle. However, performance | counters suggest that it is executing about 230 million instructions per second, which, | from my experience thus far, is pretty much the limit of a single-threaded application. | Roughly the same numbers are reported for the strand handling the interrupts (the two are | on different cores, so there is no competition for shared resources). The NIC is reading | at 700Mbps, so the network is not the bottleneck.
| I'm having a hard time putting all of this information together, as there is no clear | bottleneck. Also, I think there is a more general issue here: how can one interpret | per-strand mpstat numbers, as the resources available to a strand change dynamically with | the load on a core? The bottleneck is arguably code path length, as you're seeing almost exactly one thread's worth of CPU. The way to measure performance of an app which uses TCP is to write a script that uses snoop output or wireshark "save as CSV" data, and count request-response pairs per second (TPS, in the computer science sense of the term), and get the latency,total response time, transfer time ant BPS throughput by doing this calculation: request time -> t0 first response -> t2 last response -> t2 and then compute: latency = t1 - t0 transfer time = t2 - t1 total response time (R) = latency + transfer time bytes/second = bytes / transfer time think time = t2 from previous transaction - t0 You should see response time R grow slowly until something saturates, when it will head upwards like the handle of a hockey stick. Then report R versus TPS as a graph, This is traditionally called the hockey-stick curve. That will tell you when to add more instances of the program or buy more machines (;-)) Feel free to email me directly. -- dave (who went to UW as an undergrad) c-b -- David Collier-Brown | Always do right. This will gratify Sun Microsystems, Toronto | some people and astonish the rest [EMAIL PROTECTED] | -- Mark Twain cell: (647) 833-9377, bridge: (877) 385-4099 code: 506 9191# _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
