On Sat, 27 Aug 2005 22:58, Arjan van de Ven wrote: > > I'm asking for some kind of an authoritative answer > > quite urgently. What is the optimum thread amount on 2 CPU SMP system > > running Linux ? > > context switching in linux isn't THAT expensive compared to some other > operating systems, but it's not free either. > The optimum is obviously 2 threads, one for each cpu that processes your > network service in a state machine like way. This is why thttpd beats > apache by 10x if not more.
On a current model processor (P4 3Ghz) the current 2.6 kernel can do about 700,000 context switches per second with processes if they do nothing but switch, and perhaps slightly faster with threads. Each context switch, therefore, is quite cheap to perform. However you're unlikely to perform more than 10,000 context switches per second with real workloads and the switch itself contributes a measurable, but not performance limiting, impact. The more cpu bound your threads are the less context switches you'll perform. Fork is quite a bit more expensive. I don't have current figures on fork, but if you only fork once it shouldn't be a problem. Cheers, Con - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
