24.10.3. gem5 m5out/stats.txt file
This file contains important statistics about the run:
cat "$(./getvar --arch aarch64 m5out_dir)/stats.txt"
Whenever we run m5 dumpstats or when fs.py and se.py are exiting (TODO other scripts?), a section with the following format is added to that file:
---------- Begin Simulation Statistics ---------- [the stats] ---------- End Simulation Statistics ----------
That file contains several important execution metrics, e.g. number of cycles and several types of cache misses:
system.cpu.numCycles system.cpu.dtb.inst_misses system.cpu.dtb.inst_hits
For x86, it is interesting to try and correlate numCycles with:
In LKMC f42c525d7973d70f4c836d2169cc2bd2893b4197 gem5 5af26353b532d7b5988cf0f6f3d0fbc5087dd1df, the stat file for a C hello world:
./run --arch aarch64 --emulator gem5 --userland userland/c/hello.c
which has a single dump done at the exit, has size 59KB and stat lines of form:
final_tick 91432000 # Number of ticks from beginning of simulation (restored from checkpoints and never reset)
We can reduce the file size by adding the ?desc=False magic suffix to the stat flie name:
--stats-file stats.txt?desc=false
as explained in:
gem5.opt --stats-help
and this reduces the file size to 39KB by removing those excessive comments:
final_tick 91432000
although trailing spaces are still prse
We can further reduce this size by removing spaces from the dumps with this hack:
ccprintf(stream, " |%12s %10s %10s",
ValueToString(value, precision), pdfstr.str(), cdfstr.str());
} else {
- ccprintf(stream, "%-40s %12s %10s %10s", name,
- ValueToString(value, precision), pdfstr.str(), cdfstr.str());
+ ccprintf(stream, "%s %s", name, ValueToString(value, precision));
+ if (pdfstr.rdbuf()->in_avail())
+ stream << " " << pdfstr.str();
+ if (cdfstr.rdbuf()->in_avail())
+ stream << " " << cdfstr.str();
if (descriptions) {
if (!desc.empty())
and after that the file size went down to 21KB.