Hi, I have faced this issue in non-FS mode in the past and it always eventually boiled down to two things: 1. If you running your jobs in a cluster - it is possible that the ld.so.cache is different in each host. This means that your simulations will be slightly different because of the libraries loaded by gem5. If you are not trying your simulations on job clusters, then ignore this point. 2. There is a memory leak - this is getting triggered in one way when you don’t have debug flags on and another way when you do. Solution is to run your simulation with a tool like valgrind to detect them. It’s often easier to find the code line where this is getting triggered by running valgrind on a debug gem5 build.
Thanks, Srikant On Fri, Sep 27, 2024 at 8:28 AM Hossam ElAtali via gem5-users < gem5-users@gem5.org> wrote: > Hi Luis, > > I think I misspoke when I said full-system, since there are no cpus in the > memtest.py configuration. Only the MemTest objects that generate reads and > writes. Are you saying the only source of randomness is whatever generates > the reads/writes? So the caches, mem controller, DRAM model, etc. do not > introduce any randomness? > > For runs with CPU models, I understand how KVM models are > non-deterministic, but is there a way to make other models (e.g. o3) > deterministic as well (or are they deterministic by default)? > > Best, > Hossam > ------------------------------ > *From:* LUIS BERTRAN ALVAREZ <luis.bertran-alva...@lirmm.fr> > *Sent:* Friday, September 27, 2024 2:39:41 AM > *To:* The gem5 Users mailing list <gem5-users@gem5.org> > *Cc:* Hossam ElAtali <hossam.elat...@uwaterloo.ca> > *Subject:* Re: [gem5-users] Reproducible/deterministic runs > > > Hi Hossam, > > > From what I understand you modified the memtest.py to run full-system. > Which CPU models are you using to boot the OS? KVM CPU models are not > deterministic. If you still want to bypass your cache system to avoid > longer booting times you can use the non-caching simple CPU model > (deterministic). > > Best, > Luis > > > Le 27/09/2024 à 01:04, Hossam ElAtali via gem5-users a écrit : > > Hi, > > I wanted to ask if there is a way to make full-system runs deterministic. > I tried running with faketime set at a fixed date and time (to possibly > trick any rng seeds) but that doesn't help. > > The reason I'm asking is because of the following situation I run into. I > have a modified gem5 and when I run the memtest.py config with gem5.opt, I > get a write/read mismatch at a certain point. When I rerun with debug flags > on, the mismatch doesn't occur (or occurs earlier/later). I also tried the > following: > > Let's say the mismatch is caught at tick 1000 (for demonstrative > purposes). If I run... > > ./build/X86/gem5.opt -re --silent-redirect -d "test" > configs/example/memtest.py -f 0 -c 2:1:1:1 -t 2:1:1:1:3 > > ...or... > > ./build/X86/gem5.opt -re --silent-redirect -d "test" > --debug-flags=CacheAll,MemTest --debug-file=dbg --debug-start=5000 > configs/example/memtest.py > -f 0 -c 2:1:1:1 -t 2:1:1:1:3 > > ...I get a mismatch at tick 1000 (before tracing starts in the second > case). If I run... > > ./build/X86/gem5.opt -re --silent-redirect -d "test" > --debug-flags=CacheAll,MemTest --debug-file=dbg --debug-start=600 > configs/example/memtest.py -f 0 -c 2:1:1:1 -t 2:1:1:1:3 > > ...I don't get a mismatch at tick 1000 and the simulation continues past > that point (and might find a different mismatch afterwards). > > So is there any way to make a run completely deterministic so these > differences don't occur? That way I can run gem5 quickly without tracing > until I hit a mismatch, then rerun with tracing enabled right before that > point. Thanks a lot for your help. > > Best, > Hossam > > _______________________________________________ > gem5-users mailing list -- gem5-users@gem5.org > To unsubscribe send an email to gem5-users-le...@gem5.org > > _______________________________________________ > gem5-users mailing list -- gem5-users@gem5.org > To unsubscribe send an email to gem5-users-le...@gem5.org >
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