On Mon, August 6, 2012 9:17 am, Andreas Hansson wrote: > Hi everyone, > > A bit more detail on the mysterious pc-simple-timing that passes in zizzer > but fails on a whole range of other systems. It turns out the zizzer stats > generated in the test run are wrong(!) > > Here's how I found this out: > > > 1) Added a flag where the stat is incremented (num_mem_refs and > store_insts in src/cpu/simple/base.cc) > > 2) Dumped on two systems with the stats .value() printed with a > dedicated flag > > 3) Compared the traces, and they match! This is where my head started > to spin... :) > > 4) Ran the pc-simple-timing manually on zizzer with the command found > in the simout and guess what: the stats are the same as on the other > systems! > > 5) Tried running the regression again with scons -j1 to avoid any odd > race conditions, but the stats that come out that way are off, suggesting > the last instruction (or at least memory access) has simply not happened > yet the moment the stats are dumped. Odd to say the least. > > I have massaged the tests/SConscript to not use scons Execute command, but > instead subprocess.call, and with this change the regressions on zizzer > also fail. > > In conclusion, either scons or gem5 is doing something odd here. Any scons > ninja out there that has any idea? I tried adding a sleep of 10 s before > and after, but that does not seem to help. Could it be related to some bug > in drain? > > Perhaps we can bump the scons version on zizzer just in case? >
I was recently testing a patch related to x86 when I also noticed the problem and the stats actually matched the ones that you had posted earlier. I think it is some case similar to x86 cpuid instruction. Steve had mentioned another instruction for which he saw difference in traces from two different runs. I tried to figure if there was something wrong, but was not able to. I think if there was some problem with scons / dumping of stats, we would have seen this problem occur with other tests as well. -- Nilay _______________________________________________ gem5-dev mailing list [email protected] http://m5sim.org/mailman/listinfo/gem5-dev
