George Anzinger a écrit :
that's just the profiling interrupt hitting them. You should not
analyze irq-safe code with a non-NMI profiling interrupt.
CLI/STI is extremely fast. (In fact in the -rt tree i'm using them
within mutexes instead of preempt_enable()/preempt_disable(), because
they are faster and generate less register side-effect.)
Hm... I rather thought that the cli would cause a rather large hit on
the pipeline and certainly on OOE. Is your observation based on any
particular instruction stream? Sti, on the otherhand should be fast...
Just to be exact, the 'cli' is coded as 3 instruction :
pushfq
popq (%rsp)
cli
and the 'sti' is coded as 2 instructions :
pushq (%rsp)
popfq
And 'popfq' seems to be expensive, at least on Opteron machines and if
oprofile is not completely wrong...
Eric
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