Hi Andrew,
The first guess is that possibly the cpu results in a different code path or different scheduler decisions which lengthen execution. Another possibility is that the O3 cpu as configured by the arm-detailed configuration has some issue. While this is possible it's not incredibly likely. You could try to restore from the checkpoint and run with the checker cpu. This creates a little atomic like cpu that sits next to the o3 core and verifies it's execution which might tell you if there is a bug in the o3 model. Thanks, Ali On 01.03.2012 13:04, Andrew Cebulskiwrote: > Hi, > I'm experiencing some problems that I currently am attributing to restoring from a checkpoint, then switching to an arm_detailed CPU (O3_ARM_v7a_3). I first noticed the problem due to my committed instruction counts not lining up correctly between different CPUs for a benchmark I'm running (by roughly 170M instructions). The stats below are reset right before running the benchmark, then dumped afterwards: > Atomic CPU (no checkpoint restore): system.cpu.numInsts = 476085242 > Detailed CPU (no checkpoint restore): system.cpu.committedInsts = 476128320 > system.cpu.fetch.Insts = 478463491 > Arm_detailed CPU (checkpoint restore): system.switch_cpus_1.committedInsts = 646468886 > system.switch_cpus_1.fetch.Insts = 660969371 > Arm_detailed CPU (no checkpoint restore): system.cpu.committedInsts = 476107801 > system.cpu.fetch.Insts = 491814681 > I included both the committed and fetched instructions, to see if the problem is with fetchs getting counted as committed even if they are not (i.e. insts not getting squashed). It does not seem like that is the case from the stats above...as the arm_detailed run without a checkpoint has roughly the same difference between fetched/committed instructions. I noticed that the switch arm_detailed cpu when restoring from a checkpoint lacks both a icache and dcache as children, but I read in a previous post that they are connected to fetch/iew respectively, so this is probably not the issue. I assume it's just not shown explicitly in the config.ini file... > I'm running a test right now to see if switching to a regular DerivO3CPU has the same issue. Regardless of its results, does anyone have any idea why I'm seeing roughly 170M more committed instructions in the arm_detailed CPU run when I restore from a checkpoint? I've attached my config file from the arm_detailed with checkpoint run for reference. > Here's the run command for when I use a checkpoint: > build/ARM/gem5.fast -d [dir] configs/example/fs.py -b [benchmark] -r 1 --checkpoint-dir=[chkpt-dir] --caches -s > Lastly, I'm running off of revision 8813 from 2/3/12. Let me know if you need anymore info (i.e. stats). > Thanks, > Andrew
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