The implementation in the vdso changes with the running kernel and the
hardware it runs on. You can't just copy it.
On 30/04/2019 21.46, 'Carl Mastrangelo' via mechanical-sympathy wrote:
If the kernel implementation of clock_gettime is correct, copying the
implementation in the vDSO into the JVM should be okay too, right? If
rdtsc was not stable, it should have the same problems if invoked from
either place?
On Monday, April 29, 2019 at 10:50:05 PM UTC-7, dor laor wrote:
It might be since in the past many systems did not have a stable
rdtsc and thus if the instruction is executed
on different sockets it can result in wrong answers and negative
time. Today most systems do have a stable tsc
and you can verify it from userspace/java too.
I bet it's easy to google the reason
On Mon, Apr 29, 2019 at 2:36 PM 'Carl Mastrangelo' via
mechanical-sympathy <[email protected] <javascript:>>
wrote:
This may be a dumb question, but why (on Linux) is
System.nanotime() a call out to clock_gettime? It seems
like it could be inlined by the JVM, and stripped down to the
rdtsc instruction. From my reading of the vDSO source for
x86, the implementation is not that complex, and could be
copied into Java.
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