vince, Could you make your program such it has only 1 billion instructions? I want to see if there is some correlation with counter overflows. They are actually only 31 bit on Intel.
On Fri, Mar 19, 2010 at 10:53 PM, Vince Weaver <vweav...@eecs.utk.edu> wrote: > On Thu, 18 Mar 2010, stephane eranian wrote: > >> What about your pin your thread and run it at real-time prio. Make sure >> it is non-blocking, minimal syscalls. Compare cat /proc/interrupts >> before and after >> for that CPU. >> >> But I think what we are after is the number of transitions in and out of priv >> level 3. Could be interrupts, could be syscalls, traps. I believe the walker >> runs at the current priv level. > > I did some more tests, with the attached assembly language program that > loops for 10 billion instructions. This is on a Core2 machine with 2.6.32 > and perf_events. > > > $ perf stat -e instructions:u,cycles:u,faults:u -- ./ten_billion > > Performance counter stats for './ten_billion': > > 10000000506 instructions # 2.000 IPC > 5000523251 cycles > 1 page-faults > > 1.689113069 seconds time elapsed > > > This test has no memory access at all and is less than 4kb in size, hence > the 1 page-fault to bring in the executable. > > I ran cat /proc/interrupts before and after (in a script). In the time > the test ran, there were > 13 USB interrupts > 49 ethernet interrupts > 15 hard drive interrupts > 6 NMI > 423 timer ticks > + 6 Performance counter interrupts > ===== > 512 interrupts > > The retired instruction counter reported 506 extra instructions... so > possibly NMI or perf counter interrupts don't count (or are the same > thing). This makes it look like much of the "non-determinism" can be > attributed solely to interrupts. It's a shame there isn't an easy way > that I can find for getting this count on a per-process basis. > > I should next make a memory heavy test to see how that changes things. > > Vince > > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
