# Benchmarking / profiling cache use
**URL:** https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260
**Category:** General Usage
**Tags:** question, performance
**Created:** [November 23, 2017, 1:06am UTC](https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260 "2017-11-23T01:06:06Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)
#### Post date: [November 23, 2017, 1:06am UTC](https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260/1 "2017-11-23T01:06:06Z")
Hi,
I wanted to profile cache misses on some code of mine. I appear to be incapable of eyeballing the hardware prefetcher, and wanted to see whether some explicit prefetches improve my code. These are kinda accessible via something like:
```julia
#this is for read-data that is needed soon.
#maybe experiment with different locality values?
#prefetch on instruction cache crashes julia during compilation. meh, not needed anyway.
@inline function prefetch(address)
Base.llvmcall(("declare void @llvm.prefetch(i8* , i32 , i32 , i32 )",
"call void @llvm.prefetch(i8 * %0, i32 0, i32 0, i32 1)
ret void"), Void, Tuple{Ptr{Int8}}, convert(Ptr{Int8},address))
end
```
So, how do you people measure e.g. L1 misses in julia code?
Should I try static-julia and (linux-) perf?
If this is indeed the only reasonable way, should I then write my sample code with a @Base.ccallable ju\_main() function, compile into shared library and write a tiny piece of C code that calls the library’s ju\_main? Can I use static-julia to build with debug symbols?
PS. My code does a graph traversal; links are offsets into a fixed array. This is should be very bad for the cache. But I need proper tests before I should consider fancy memory layouts; and a couple explicit prefetches are a much lower effort fix than cache-oblivious stuff.
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [November 23, 2017, 9:02am UTC](https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260/2 "2017-11-23T09:02:05Z")
Perhaps [GitHub - carnaval/LinuxPerf.jl](https://github.com/carnaval/LinuxPerf.jl) could be of use.
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### Author:  [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)
#### Post date: [November 23, 2017, 12:17pm UTC](https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260/3 "2017-11-23T12:17:11Z")
Thank you! Google completely failed me there.
This tool is absolutely fantastic; just kindly asking the kernel is obviously much better than a rube-goldberg construction to pass compiled julia into command line tools.
At some point there should be a sticky post / wiki describing these tricks. Carnaval’s IACA.jl also looks extremely interesting.
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### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [November 23, 2017, 12:23pm UTC](https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260/4 "2017-11-23T12:23:40Z")
I think this is a continued version of Carnavals IACA: [https://github.com/vchuravy/IACA.jl](https://github.com/vchuravy/IACA.jl)
---
### Author:  [@system](https://discourse.julialang.org/u/system)
#### Post date: [November 24, 2017, 12:23pm UTC](https://discourse.julialang.org/t/benchmarking-profiling-cache-use/7260/5 "2017-11-24T12:23:54Z")
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