Minor factual errors regarding systemtap [LWN.net]

Minor factual errors regarding systemtap

Posted Aug 7, 2007 21:20 UTC (Tue) by oak (subscriber, #2786)
In reply to: Minor factual errors regarding systemtap by fuhchee
Parent article: On DTrace envy

A colleague did a quick/ad-hoc test of the recent ARM port of Systemtap
and a single Systemtap syscall probe seems to have about as much
performance hit for the system as the whole LTT(ng) thing. Does this
result sound right (LTT uses static probe points whereas Systemtap uses
dynamic kprobe + has its own overhead on top of that)?

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Minor factual errors regarding systemtap

Posted Aug 7, 2007 22:10 UTC (Tue) by fuhchee (subscriber, #40059) [Link]

> [on ARM a] single Systemtap syscall probe seems to have about as much
> performance hit for the system as the whole LTT(ng) thing.

Please post some details to the mailing list.

> Does this result sound right (LTT uses static probe points whereas Systemtap
> uses dynamic kprobe + has its own overhead on top of that)?

Yes, dynamic probes are significantly costly than static probe points,
but overall cost is a function that includes rate-of-hits and other
quantities. Note that the LTT static probe points will be transparently
exploitable from systemtap once this part of LTT is merged upstream,
and this should greatly reduce the performance differences.