Hello,
We noticed a bit strange behavior while doing some measurements with the riscv
bsps running on SIS.
If we run "T_get_one_clock_tick_busy" to get a base reference for busy cycles,
the values between cpu0 and other secondary cores differ by a constant value.
For example for a 200us tick time:
cpu0: 4460 cycles per tick
cpu1: 4848 cycles per tick
cpu2: 4848 cycles per tick
Results for multiple calls on the same core only differ in a few ticks.
For a 500us tick time it yields:
cpu0: 11957 cycles per tick
cpu1: 12350 cycles per tick
cpu2: 12348 cycles per tick
So, in both cases there is a constant difference of approx. 390 cyples per tick
between core0 and all other cores.
We ran the test application with "riscv-rtems6-sis -m 4 bin/test-busy-loop.elf
-freq 100 -d 25 -r"
Is this something to be expected and what could be the reason for this (e.g. in
rtems or in the SIS)?
Best regards,
Jan
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
German Aerospace Center
Institute for Software Technology | Software for Space Systems and Interactive
Visualization | Lilienthalplatz 7 | 38108 Braunschweig | Germany
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