Messages in this thread | | | Subject | Re: release 0.2 of x86 performance-monitoring counters support patch | From | Andi Kleen <> | Date | 10 Jun 1999 02:02:27 +0200 |
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mikpe@csd.uu.se (Mikael Pettersson) writes: > > > If you still want rdpmc you can leave it as a trap to kernel and simulate > > it with a read from total. > > No need to trap. (That'd be so awful that people should just do a syscall > instead.) I allow the user to register a user-space buffer with the driver. > At process resumption, I copy the counter state to this buffer. (Technique > stolen from sparc64's sys_perfctr() implementation.) The user executes > RDPMC and RDTSC, retrieves the "base" values from the buffer, and then > computes the current "virtual" 64-bit values. This should permit people > to bracket single procedure bodies or basic blocks with sampling code > without too much overhead.
Only thing that I'm missing in your nice patch is a way to access the performance counters of remote processes (so that I could hack gdb to do non intrusive profiling a la itune). Extending the ioctls could work, although a ptrace extension would be nicer.
> I'll probably do this with mmap instead, as soon as I've figured out how...
Most likely not worth it for the small amount of data.
-Andi
-- This is like TV. I don't like TV.
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