Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108

Mathieu Desnoyers
2006-09-18T14:58:51Z

* Jes Sorensen (jes@sgi.com) wrote:
> Mathieu Desnoyers wrote:
> > And about those extra cycles.. according to :
> > Documentation/kprobes.txt
> > "6. Probe Overhead
> >
> > On a typical CPU in use in 2005, a kprobe hit takes 0.5 to 1.0
> > microseconds to process. Specifically, a benchmark that hits the same
> > probepoint repeatedly, firing a simple handler each time, reports 1-2
> > million hits per second, depending on the architecture. A jprobe or
> > return-probe hit typically takes 50-75% longer than a kprobe hit.
> > When you have a return probe set on a function, adding a kprobe at
> > the entry to that function adds essentially no overhead.
> [snip]
> > So, 1 microsecond seems more like 1500-2000 cycles to me, not 50.
>
> So call it 2000 cycles, now go measure it in *real* life benchmarks
> and not some artificial I call this one syscall that hits the probe
> every time in a tight loop, kinda thing.
>
> Show us some *real* numbers please.
>

You are late (I don't blame you about it, considering the size of this thread).
It has been posted in the following email :

http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-09/msg04492.html

Mathieu

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