Fredrik Bagge Carlson (Jun 23 2022 at 05:48): Fredrik Bagge Carlson (Jun 23 2022 at 05:48):If I run
using SnoopCompile
@snoopl "func_names.csv" "llvm_timings.yaml" begin
my_code()
end
times, info = SnoopCompile.read_snoopl("func_names.csv", "llvm_timings.yaml")
sum(first, times)
Is sum(first, times) going to return approximately the total time spent by LLVM optimizing the function call?
Fredrik Bagge Carlson (Jun 23 2022 at 05:49):When I snoop on inference using @snoopi_deep, I get that about half of the compilation time is in inference. With the approach above, I get a time corresponding roughly to the other half, indicating that (if the approach is reasonable) the compilation time is roughly 50/50 inferece/LLVM
Rik Huijzer (Jun 23 2022 at 06:26):You mean LLVM compiling binary code? I heard Valentin Churavy say that it’s about 30% LLVM time
Fredrik Bagge Carlson (Jun 23 2022 at 06:36):Yeah, I'm after the percentage of total compilation time that is taken up by LLVM, since I will not attempt to reduce this any further. LLVM really dislikes some things, e.g., very large functions, so the LLVM time can be greater in some situations than others
Brian Chen (Jun 23 2022 at 13:55):Rik Huijzer said:
You mean LLVM compiling binary code? I heard Valentin Churavy say that it’s about 30% LLVM time
I think that's a rule of thumb, because I've also seen breakdowns like what @Fredrik Bagge Carlson mentioned. Large functions definitely appear to be a culprit.
Sukera (Jun 23 2022 at 17:57):either way, LLVM time is a big chunk and there's no really easy way for us to speed that up
Brian Chen (Jun 23 2022 at 17:58):Mechanisms for finer-grained application of optlevels could help. e.g. exclude "glue code" but keep optimizing hot loops, broadcasts etc. The current module-level setting is too coarse.
jar (Jun 23 2022 at 18:15):Maybe julia could add some benchmarks to the llvm benchmark tracker
https://www.npopov.com/2020/05/10/Make-LLVM-fast-again.html
http://llvm-compile-time-tracker.com/index.php
chriselrod (Jun 23 2022 at 19:10):Compile with -DENABLE_TIMINGS or uncomment:
https://github.com/JuliaLang/julia/blob/4873773d37e06d01ad13a0d55df684789ddd29ad/src/options.h#L87
chriselrod (Jun 23 2022 at 19:11):That will give you a breakdown of where time was spent whenever a Julia process exits.
chriselrod (Jun 23 2022 at 19:12):JULIA_LLVM_ARGS="-time-passes" julia
chriselrod (Jun 23 2022 at 19:12):will give you a breakdown of where LLVM spent its time.
Last updated: Oct 02 2023 at 04:34 UTC