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very strang latency result #4
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It's been a very long time since I last worked on those topics. That sounds awfully slow, true. What is the BAR and register you are reading from? Does the time differ when you read from a different Offset? |
I tried to use BAR2 and the result looks much better:
Mean | 1667.17 cycles | 795.75 ns
Mean | 1648.78 cycles | 786.98 ns However the latency result from Microsemi Switch programm is between 85ns and 140ns, could you tell me which latency do I have here(786.98 ns)? Is it the latency of CPU1 ->PCIe Switch->CPU2 -> PCIe Switch -> CPU1 or CPU1->PCIe Switch ->CPU1? |
I fear I cannot help much here without knowing lots of low-level details of your setup, sorry :( |
Hi Andre,
I am using 2 x86 Intel CPUs and one microsemi PCIe switch between them. Ubuntu 18.04 is running on both CPUs. I am sure that the PCIe-switch is right configured and PCIe driver on both CPU are also correct. But I got the following results which is very strange. Do you have some ideas about that? Thx!
TSC freq: 2095077000.0 Hz
TSC overhead: 32 cycles
Device: b3:00.1
BAR: 0
Offset: 0x0
Loops: 100000
Mean | 32612.38 cycles | 15566.20 ns
Stdd | 47215.27 cycles | 22536.29 ns
Mean | 19535.33 cycles | 9324.40 ns
Stdd | 1600.78 cycles | 764.07 ns
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