Fiasco.OC performance issues

[Sebastian Sumpf]

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



-- 
Sebastian Sumpf
Genode Labs

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