Hi L4 hackers,
I recently upgraded Fiasco.OC to SVN revision 42 and experience some pretty severe performance degradation compared to revision 40 on the Pandaboard (SMP). It seems that 'simga0' and the root task stall for 5 to 10 seconds during boot up. I tracked the issue down to be caused by the initial mapping operations, especially our root task maps all the available memory during bootstrap. Within the kernel the 'Context::xcpu_tlb_flush' is called for each mapping. The function sends an IPI (to CPU1 which is idle) and then waits for an IPI in order to signal the end of the operation. The whole operation seems to have gotten slower compared to revision 40, but I could not find many differences in the IPI-handling code. Do you have any ideas or suggestions what could cause the delay (maybe scheduling changes) and how to fix it?
Thanks,
Sebastian