--- Steve Loughran <[EMAIL PROTECTED]> schrieb:
> this is really interesting. I'd thought javac was
> unthreaded too, but
> even so you'd expect file IO to work in the other
> CPU, so get a boost
> from the second core.
>
> what happens when you try a different javac, like
> the eclipse one?
I have timed a very short compile run with different
JDKs on the same machine,
using the same OS one time with both cores enabled,
the other time with only
one core enabled.
Result: the compile run using only one core was
significantly faster than the
one using both cores. This is true with every JDK I
tried.
So this might be an ant specific phenomenom? Maybe ant
is spawning threads?
Test methodology:
=================
- Processor: Intel Core 2 Duo E6600
- OS: Ubuntu Linux 8.04 with kernel 2.6.24-11-generic
(2.6.24.3 with ubuntu specific patches)
- The number of cores has been chenged by adding
"maxcpus=1" at
the grub boot command line
- Ant 1.7.0 from ant.apache.org
- JDKs: - Sun JDK 6 Update 4
- Sun JDK 5 Update 15
- IBM JDK 6
- BEA JRockit JDK 6 Update 3
- Before every run I changed PATH to the specific JDK
location and tested
the PATH with java -version
- Then I executed ant clean ; ant compile ; ant clean
; sleep 5 ; time ant compile
This way, every file is cached in RAM before the
last compile run is executed,
which is timed.
Test results:
=============
1 core:
-------
Sun JDK 6 Update 4:
real 0m1.132s
user 0m1.032s
sys 0m0.056s
Sun JDK 5 Update 15:
real 0m1.143s
user 0m1.016s
sys 0m0.076s
IBM JDK 6:
real 0m1.135s
user 0m1.028s
sys 0m0.068s
BEA JRockit JDK 6 Update 3:
real 0m1.136s
user 0m1.064s
sys 0m0.028s
2 cores:
--------
Sun JDK 6 Update 4:
real 0m1.582s
user 0m2.428s
sys 0m0.128s
Sun JDK 5 Update 15:
real 0m1.514s
user 0m2.208s
sys 0m0.116s
IBM JDK 6:
real 0m1.439s
user 0m2.164s
sys 0m0.084s
BEA JRockit JDK 6 Update 3:
real 0m1.619s
user 0m2.500s
sys 0m0.124s
JDK Versions:
-------------
$ java -version
java version "1.6.0_04"
Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
Java HotSpot(TM) Server VM (build 10.0-b19, mixed
mode)
$ java -version
java version "1.5.0_15"
Java(TM) 2 Runtime Environment, Standard Edition
(build 1.5.0_15-b04)
Java HotSpot(TM) Server VM (build 1.5.0_15-b04, mixed
mode)
$ java -version
java version "1.6.0"
Java(TM) SE Runtime Environment (build
pxi3260-20071123_01)
IBM J9 VM (build 2.4, J2RE 1.6.0 IBM J9 2.4 Linux
x86-32 jvmxi3260-20071121_15015 (JIT enabled)
J9VM - 20071121_015015_lHdSMR
JIT - r9_20071121_1330
GC - 20071031_AA)
JCL - 20071118_01
$ java -version
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
BEA JRockit(R) (build
R27.5.0-110-94909-1.6.0_03-20080204-1558-linux-ia32,
compiled mode)
CPU with one core enabled:
--------------------------
$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 CPU 6600 @
2.40GHz
stepping : 6
cpu MHz : 1600.000
cache size : 4096 KB
physical id : 0
siblings : 1
core id : 0
cpu cores : 1
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep
mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr
sse sse2 ss ht tm pbe nx lm constant_tsc up
arch_perfmon pebs bts pni monitor ds_cpl vmx est tm2
ssse3 cx16 xtpr lahf_lm
bogomips : 4791.85
clflush size : 64
CPU with two cores enabled:
---------------------------
$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 CPU 6600 @
2.40GHz
stepping : 6
cpu MHz : 1600.000
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep
mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr
sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon
pebs bts pni monitor ds_cpl vmx est tm2 ssse3 cx16
xtpr lahf_lm
bogomips : 4791.87
clflush size : 64
processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 CPU 6600 @
2.40GHz
stepping : 6
cpu MHz : 1600.000
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep
mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr
sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon
pebs bts pni monitor ds_cpl vmx est tm2 ssse3 cx16
xtpr lahf_lm
bogomips : 4788.35
clflush size : 64
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