Hi Yingying,
I saw your email on gem5 users. Now that I look at your statistics, I may
have the same problem as your are seeing, because I was also seeing
strangely flat IPC values for  lot of the benchmarks. It was not happening
for all benchmarks (I was running parsec on X86), but I was it in most of
them. By the way, I had the same issue both for fastforwarding and
checkpointing.
I also have a lot of "nan" IPC when I increase the number of cores
simulated. For example, if I use 4 cores and 4 threads , I was seeing that
2 of the cores had "nan" IPC most of the time. I thought it could be about
how the kernel schedules threads on the cores, so I tried "setting
affinity" but it did not work either.
http://www.mail-archive.com/[email protected]/msg08461.html
http://www.mail-archive.com/[email protected]/msg08465.html

Do you know how to use debug flags and localApic? Maybe we can try to debug
simultaneously and solve it faster.
Best,
Fulya


On Fri, Sep 27, 2013 at 2:42 PM, Yingying Tian <[email protected]>wrote:

> To whom it may concern,
>
> Sorry for a long email...
>
> I tried to run gem5/X86/FS with checkpoint on Ubuntu. I noticed that
> whenever I restored from checkpoint using o3+cache or even timing+cache,
> the simulation freezed. The output of the benchmark, which I should be able
> to see from system.pc.com_1.terminal freezed like this:
>
> *==== m5 slave terminal: Terminal 0 ====*
> *icount=-4128687954, cycl*
> *
> *
> This is some random output I printed myself within the benchmark. The word
> cycle was not even printed out completely. Even ignoring the output of the
> benchmark, the simulation never ends (with very small input size).
>
> I tried different combination of the following things:
> different versions of gem5: stable and dev (latest)
> kernels: 2.6.22.smp & 2.6.28.smp
> disk-images: my own spec-benchmark image, the default x86.img from the
> website, the default parsec-x86 from the website, and my own parsec.img;
> different mem-size: 128MB, 512MB, 2GB
> ways to create checkpoint: m5 checkpoint in rcS, m5 checkpoint in the
> shell; take-checkpoints option in the command line;
>
> None of them works. I found a previous bug report (
> http://flyspray.gem5.org/index.php?do=details&task_id=7) and I felt the
> problem was similar to this one. However Joel Hestness told me that it had
> been solved in the version I used.
>
> Then I used statDump to check the simulation results regularly. And here
> is an example of a 2core workloads: spec benchmark 400.perlbench on core0
> and 429.mcf on core1.
>
> system.switch_cpus0.ipc_total                0.396695
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.247679
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.522044
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.378344
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.509733
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.400118
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.846664
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.127269
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.560433
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.256860
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.585251
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.336722
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.507201
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.403585
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.395082
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.026726
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.401066
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.015240
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.309344
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.052741
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.051074
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.361373
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.040542
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.050384
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.423759
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.046418
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.850809
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.037467
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.523393
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.045001
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.445640
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                0.993358
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.579385
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.033880
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.526860
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.038723
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.535044
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.046553
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.489415
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.035276
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.598916
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.050906
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.537702
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.050915
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.048455
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.041851
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.375907
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.047675
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.475280
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.045908
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.538461
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.052359
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.585786
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.029951
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.576559
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.040542
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.592840
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.045945
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.619702
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.056207
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.623229
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.025213
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.616485
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.365757
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.612818
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.482195
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.552020
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.475002
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.505007
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.479304
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.459360
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.442754
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.517478
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.349029
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.517517
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.451960
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.491960
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.475903
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.573747
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.518406
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.581939
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.478804
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.541246
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.508847
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.553826
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.447361
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.210487
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.489019
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.502452
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.470074
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                     nan
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.506439
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.519539
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.526431
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.540206
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.491766
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.554450
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.335522
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.580120
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.497462
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.572519
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.512147
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.566786
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.524408
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.559435
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.522306
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.558261
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.492940
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.549201
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.493601
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.534580
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.434092
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.242578
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.521245
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                0.498063
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.474697
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                1.194256
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                1.791502
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                2.357143
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                2.357142
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                2.353913
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                2.357143
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                2.357143
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                2.354863
>   # IPC: Total IPC of All Threads
> system.switch_cpus0.ipc_total                2.354693
>   # IPC: Total IPC of All Threads
> system.switch_cpus1.ipc_total                2.357142
>   # IPC: Total IPC of All Threads
>
> and for the rest of the results, ipc of each core is always 2.35xxx. (2.35
> for mcf is not reasonable). Then I tried different 2-core workloads,
> noticing that after a while the ipc of each core became 2.35xxx for all the
> workloads.
>
> I have been bothered by this issue for a while. And my colleagues cannot
> make it work either. I am not sure if I made any stupid mistakes or
> something else? Could you please give me any suggestions? Thank you in
> advance.
>
> Best,
> Yingying
>
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