On Linux, you'll probably also need a
static {
System.loadLibrary("nameofsofilethathascyclecounterdoto");
}
in CycleCounter.java.
- Godmar
>
> >
> > I've had similar problems measuring bandwidth. The greatest difficulty was the
> > limited resoution of the available timers. It's a darn shame that a high
> > resolution counter isn't available given all these fancy hardware. Milliseconds!
> > Pah! You can do an awful lot in a millisecond. Ever since the Pentium was
> > release there have been high resolution counters available - anyone written some
> > code to access them ? - back then it was all restricted access only! Does Intel
> > give a damn now ?
> >
>
> Here you go.
>
> - Godmar
>
> // ------------------------------------------------------------------------
> // CycleCounter.java
> package kaffeos.sys;
>
> /**
> * Give Java programs access to the cycle counter on Pentium PCs.
> */
> public class CycleCounter
> {
> /**
> * read the current cycle counter
> */
> public static native long read();
> }
>
> /* ------------------------------------------------------------------------
> CycleCounter.c
> */
> /*
> * Read the 64-bit timestamp counter (TSC) register.
> * Works only on Pentium and higher processors,
> * and in user mode only if the TSD bit in CR4 is not set.
> */
> #if defined(i386)
> #if HAVE_RDTSC
> #define get_tsc() \
> ({ \
> unsigned long low, high; \
> asm volatile("rdtsc" : "=d" (high), "=a" (low)); \
> ((unsigned long long)high << 32) | low; \
> })
> #else
> #define get_tsc() \
> ({ \
> unsigned long low, high; \
> asm volatile( \
> ".byte 0x0f; .byte 0x31" \
> : "=d" (high), "=a" (low)); \
> ((unsigned long long)high << 32) | low; \
> })
> #endif
> #else
> #define get_tsc() 0
> #endif
>
> #include <jni.h>
>
> jlong
> Java_kaffeos_sys_CycleCounter_read(JNIEnv *env, jclass counterclass)
> {
> return (jlong)get_tsc();
> }
> ~
>
>
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