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SubjectRe: Performance analysis of Linux Kernel Markers 0.20 for 2.6.17
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On Sat, 2006-09-30 at 23:42 -0400, Mathieu Desnoyers wrote:
> * Nicholas Miell (nmiell@comcast.net) wrote:
> >
> > Has anyone done any performance measurements with the "regular function
> > call replaced by a NOP" type of marker?
> >
>
> Here it is (on the same setup as the other tests : Pentium 4, 3 GHz) :
>
> * Execute an empty loop
>
> - Without marker
> NR_LOOPS : 10000000
> time delta (cycles): 15026497
> cycles per loop : 1.50
>
> - With 5 NOPs
> NR_LOOPS : 100000
> time delta (cycles): 300157
> cycles per loop : 3.00
> added cycles per loop for nops : 3.00-1.50 = 1.50
>
>
> * Execute a loop of memcpy 4096 bytes
>
> - Without marker
> NR_LOOPS : 10000
> time delta (cycles): 12981555
> cycles per loop : 1298.16
>
> - With 5 NOPs
> NR_LOOPS : 10000
> time delta (cycles): 12983925
> cycles per loop : 1298.39
> added cycles per loop for nops : 0.23
>
>
> If we compare this approach to the jump-over-call markers (in cycles per loop) :
>
> NOPs Jump over call generic Jump over call optimized
> empty loop 1.50 1.17 2.50
> memcpy 0.23 2.12 0.07
>
>
>
> Mathieu

What about with two NOPs (".byte 0x66, 0x66, 0x90, 0x66, 0x90" - this
should work with everything) or one (".byte 0x0f, 0x1f, 0x44, 0x00,
0x00" - AFAIK, this should work with P6 or newer).

(Sorry, I should have mentioned this the first time.)

--
Nicholas Miell <nmiell@comcast.net>

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