Messages in this thread | | | Date | Sun, 1 Oct 2006 11:33:17 -0400 | From | Mathieu Desnoyers <> | Subject | Re: Performance analysis of Linux Kernel Markers 0.20 for 2.6.17 |
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* Nicholas Miell (nmiell@comcast.net) wrote: > 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.) >
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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