Dear Jim/All, You are correct, What I was talking is not clear to. Scenario: ======= We are building high preformance trading systems, which is processing 10000 transactions per second. Our trade information traverse through about 5-7 hops. We are trying to achive about 10-50ms latencey in a execution for 90% of the transactions. Although this may sound extreme, the trading requirements are getting more & more tighter due to Electronic order generators coming into the picture. Currently there is very wide spread of the latency of the system (sometime going to 700ms) All the applciations are written the tight latency requirements in mind( No blocking call / No synchronous I/O etc..) In fact we have been able to succefully implement & benchmark the system in Solaris 5.9 with RT scheduling and CPU binding with a very tight ( < 30 ms) latency for 90%. But we are struggeling to narrow down the numbers for Linux. Was it a bad choice to select Linux for RT applications. What can we do to tune the 2.6 kernel to improve the figures. 1. When HZ=1000, Latencey < 2ms (best case) 2. When HZ=2000, Latencey < 1ms (best case) 3. Real Time or Low Latancey Patching Are there any other tuning nobe other than HZ....?
I must say, Im somewhat puzzled .. considering 1- trading system + 2- a 2.6.9 RHEL kernel, this seems like a requirement put upon you by marketing in the hope of making it more palatable to big (corporate) buyers. Perhaps that explains your need to 'turn the HZ knob to eleven', when its only labeled to 10. trading system does sound like soft-RT. The plane doesnt crash if youre 100ms late on the rudder / flaps / important things. Why arent you more concerned with thruput ? Youre clearly killing thruput when the system cant even take care of its own business (at HZ=4000)
Yh. I could not start the System with 4000HZ. I just got stucked at ...TIMER APIC initialization. Now running with 2000 HZ. Seems to be kernel is somewhat stable, not sure.
>> >> CONFIG_PREEMPT_RT is in recent mainline, as is PREEMPT_VOLUNTARY > I have settled PREEMPT_RT option what is settled ? Im pretty sure 2.6.9 had no PREEMPT_RT icbw.
Yes, You are correct. I have just truned on CONFIG_PREEMPT only. Not RT. -- Tharindu Rukshan Bamunuarachchi all fabrications are subject to decay -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
