lkml.org 
[lkml]   [2006]   [Oct]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Performance analysis of Linux Kernel Markers 0.20 for 2.6.17
* 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


OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg
Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-10-01 17:35    [W:0.071 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site