(RADIATOR) counterintuitive benchmarks

[Tariq Rashid]

i've started on somebenchamreking of radius servers - after some initial trouble withf orking and then threads.

despite the fact that the received wisdom is that threading does not allow you to write faster clients that hit a server harder (clients, with each thread doing the request and timing the responce) - there does in fact appear to be some performance gain from threads on single-cpu clients - probably because other threads can "get in" when between other threads in less time than it takes to create single sequential threads. if anyone can throw some light on this i'd be grateful. the server is currently single-threaded (radiator, freeradius will also be tested next).

anyway - the puzzle i'm facing is that i'm apparently seeing odd results? i'm seeing a typical graph of response time against request rate. as the request rate goes from 1/sec to higher rates... the responce time is initially very flat at 0.075secs... then at a specific rate it climbs almost linearly to a peak ... and then plateus at this max. the max may be due to client or server limits... i haven't investigated yet.

however... it appears that different client machine speeds give different points at which the responce time starts to climb from its initial rapid baseline. you may suggest that the clients are reching their thread scheduling or network limits at different request rates. but the faster machine (dual 3Ghz Zeon) seem to reach this poiont before the slower ones (amd 800Mhz single cpu)? how can this be? 

could it be that the faster machine actually manage to switch threads faster and so do in fact hit the radius server harder?

i don't want to use non-standard logging options (such as Trace -1) as i need to emuklate the normal trace 5 to a file which is used on live servers.

thoughts appreciated.

tariq

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