* Nicholas Miell ([email protected]) wrote:
> On Sat, 2006-09-30 at 23:42 -0400, Mathieu Desnoyers wrote:
> > * Nicholas Miell ([email protected]) 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.)
>
Hi,
The tests I made were with :
#define GENERIC_NOP1 ".byte 0x90\n"
#define GENERIC_NOP4 ".byte 0x8d,0x74,0x26,0x00\n"
#define GENERIC_NOP5 GENERIC_NOP1 GENERIC_NOP4
Now with the tests you ask for :
* Execute an empty loop
- 2 NOPs ".byte 0x66, 0x66, 0x90, 0x66, 0x90"
NR_LOOPS : 100000
time delta (cycles): 200190
cycles per loop : 2.00
cycles per loop for nops : 2.00-1.50 = 0.50
- 1 NOP "0x0f, 0x1f, 0x44, 0x00, 0x00"
NR_LOOPS : 100000
time delta (cycles): 300172
cycles per loop : 3.00
cycles per loop for nops : 3.00-1.50 = 2.50
* Execute a loop of memcpy 4096 bytes
- 2 NOPs ".byte 0x66, 0x66, 0x90, 0x66, 0x90"
NR_LOOPS : 10000
time delta (cycles): 12981293
cycles per loop : 1298.13
cycles per loop for nops : 1298.16-1298.13=0.03
- 1 NOP "0x0f, 0x1f, 0x44, 0x00, 0x00"
NR_LOOPS : 10000
time delta (cycles): 12985590
cycles per loop : 1298.56
cycles per loop for nops : 0.43
Mathieu
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