Tharindu Rukshan Bamunuarachchi wrote: > 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 Try the RT patches that can be found at http://people.redhat.com/mingo/realtime-preempt/ > > 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 Sorry I overlooked the previous posts so I am not sure who made the statement above, but it is not accurate. PREEMPT_VOLUNTARY is not the ame as CONFIG_PREEMPT_RT. CONFIG_PREEMPT_RT requires additional patches that I pointed to above. >> > 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. > > > > -- kr -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
