A fine-grained micro-benchmark intended to investigate micro-architectural details of a target CPU, or to precisely benchmark small functions in a repeatable manner.
This project is very much a work-in-progress, and is currently in a very early state with limited documentation and testing. Pull requests and issues welcome.
The uarch-bench project is a collection of micro-benchmarks that try to stress certain microarchitectural features of modern CPUs and a framework for writing such benchmarks. Using libpfc you can accurately track the value of Intel performance counters across the benchmarked region - often with precision of a single cycle.
At the moment it supports only x86, using mosty assembly and a few C++ benchmarks. In the future, I'd like to have more C or C++ benchmarks, allowing coverage (in prinicple) of more platforms (non-x86 assembly level benchmarks are also welcome). Of course, for any non-asm benchmark, it is possible that the compiler makes a transformation that invalidates the intent of the benchmark. You could detect this as a large difference between the C/C++ and asm scores.
Of course, these have all the pitfalls of any microbenchmark and are not really intended to be a simple measure of the overall performance of any CPU architecture. Rather they are mostly useful to:
- Suss out changes between architectures. Often there are changes to particular microarchitectural feature that can be exposed via benchmarks of specific features. For example, you might be able to understand something about the behavior of the store buffer based on tests that excercise store-to-load forwarding.
- Understand low-level performance of various approaches to guide implemenation of highly-tuned algorithms. For the vast majority of typical development tasks, the very low level information provided by these benches is essentially useless in providing any guidance about performance. For some very specific tasks, such as highly-tuned C or C++ methods or hand-written assembly, it might be useful to characterize the performance of, for example, the relative costs of aligned and unaligned accesses, or whatever.
- Satisfy curiosity for those who care about this stuff and to collect the results from various architectures.
- Provide a simple, standard way to quickly do one-off tests of some small assembly or C/C++ level idioms. Often the test itself is a few lines of code, but the cost is in all the infrastructure: implementing the timing code, converting measurements to cycles, removing outliers, running the tests for various parameters, reporting the results, whatever. This project aims to implement that infrastructure and make it easy to add your own tests (not complete!).
You need some C++ compiler like
clang++, but if you are interested in this project, you probably already have that. Beyond that, you need
nasm and perhaps
msr-tools on Intel platforms (used to as a backup method to disable turbo-boost if you aren't using
intel_pstate driver). On Debian-like systems, this should do it:
sudo apt-get install nasm sudo apt-get install msr-tools
This project has submodules, so it is best cloned with the
--recursive flag to pull all the submodules as well:
git clone --recursive https://github.com/travisdowns/uarch-bench
If you've already cloned it without
--recursive, this should pull in the submodules:
git submodule update --init
Then just run
make in the project directory. If you want to modify any of the make settings, you can do it directly in
config.mk or in a newly created local file
local.mk (the latter having the advantage that this file is ignored by git so you won't have any merge conflicts on later pulls and won't automatically commit your local build settings).
Ideally, you run
./uarch-bench.sh as root, since this allows the permissions needed to disable frequency scaling, as well as making it possible use
USE_LIBPFC=1 mode. If you don't have root or don't want to run a random project as root, you can also run it has non-root as
uarch-bench (i.e., without the wrapper shell script), which will still work with some limitations. There is current an open issue for making non-root use a bit smoother.
./uarch-bench.sh after building. The script will generally invoke
sudo to prompt you for root credentials in order to disable frequency scaling (either using the
no_turbo flag if
intel_pstate governor is used, or
You can also run the binary as
./uarch-bench directly, which doesn't require sudo, but frequency scaling won't be automatically disabled in this case (you can still separately disable it prior to running
Command Line Arguments
uarch-bench --help to see a list and brief description of command line arguments.
One key to more reliable measurements (especially with the timing-based counters) is to ensure that there is no frequency scaling going on.
Generally this involves disabling turbo mode (to avoid scaling above nominal) and setting the power saving mode to performance (to avoid scaling below nominal). The uarch-bench.sh script tries to do this, while restoring your previous setting after it completes.
$ sudo ./uarch-bench.sh Driver: intel_pstate, governor: performance Vendor ID: GenuineIntel Model name: Intel(R) Core(TM) i5-5300U CPU @ 2.30GHz Succesfully disabled turbo boost using intel_pstate/no_turbo Using timer: clock Welcome to uarch-bench (caa208f-dirty) Supported CPU features: SSE3 PCLMULQDQ VMX SMX EST TM2 SSSE3 FMA CX16 SSE4_1 SSE4_2 MOVBE POPCNT AES AVX RDRND TSC_ADJ BMI1 HLE AVX2 BMI2 ERMS RTM RDSEED ADX INTEL_PT Pinned to CPU 0 Median CPU speed: 2.193 GHz Running benchmarks groups using timer clock ** Running group basic : Basic Benchmarks ** Benchmark Cycles Nanos Dependent add chain 1.00 0.46 Independent add chain 0.26 0.12 Dependent imul 64->128 3.00 1.37 Dependent imul 64->64 3.00 1.37 Independent imul 64->128 1.01 0.46 Same location stores 1.00 0.46 Disjoint location stores 1.00 0.46 Dependent push/pop chain 5.00 2.28 Independent push/pop chain 1.00 0.46 Simple addressing pointer chase 4.00 1.83 Complex addressing pointer chase 5.01 2.28 Finished in 556 ms (basic) ** Running group memory/load-parallel : Parallel loads from fixed-size regions ** Benchmark Cycles Nanos 16-KiB parallel load 0.53 0.24 24-KiB parallel load 0.52 0.24 30-KiB parallel load 0.53 0.24 31-KiB parallel load 0.53 0.24 32-KiB parallel load 0.52 0.24 33-KiB parallel load 0.54 0.24 34-KiB parallel load 0.55 0.25 35-KiB parallel load 0.56 0.26 40-KiB parallel load 1.34 0.61 48-KiB parallel load 2.01 0.92 56-KiB parallel load 2.01 0.92 64-KiB parallel load 2.01 0.92 80-KiB parallel load 2.06 0.94 96-KiB parallel load 2.18 0.99 112-KiB parallel load 2.27 1.03 128-KiB parallel load 2.24 1.02 196-KiB parallel load 2.72 1.24 252-KiB parallel load 3.75 1.71 256-KiB parallel load 3.68 1.68 260-KiB parallel load 0.53 0.24 384-KiB parallel load 4.34 1.98 512-KiB parallel load 5.19 2.36 1024-KiB parallel load 5.64 2.57 2048-KiB parallel load 6.16 2.81 Finished in 7050 ms (memory/load-parallel) ** Running group memory/store-parallel : Parallel stores to fixed-size regions ** Benchmark Cycles Nanos 16-KiB parallel store 1.00 0.46 24-KiB parallel store 1.00 0.46 30-KiB parallel store 1.17 0.53 31-KiB parallel store 1.00 0.46 32-KiB parallel store 1.00 0.46 33-KiB parallel store 1.15 0.52 34-KiB parallel store 1.32 0.60 35-KiB parallel store 1.29 0.59 40-KiB parallel store 4.32 1.97 48-KiB parallel store 6.20 2.83 56-KiB parallel store 6.23 2.84 64-KiB parallel store 6.10 2.78 80-KiB parallel store 6.25 2.85 96-KiB parallel store 6.24 2.84 112-KiB parallel store 6.26 2.85 128-KiB parallel store 6.26 2.86 196-KiB parallel store 6.36 2.90 252-KiB parallel store 6.71 3.06 256-KiB parallel store 6.75 3.08 260-KiB parallel store 1.01 0.46 384-KiB parallel store 7.78 3.55 512-KiB parallel store 8.67 3.95 1024-KiB parallel store 9.59 4.37 2048-KiB parallel store 9.97 4.55 Finished in 14892 ms (memory/store-parallel) ** Running group memory/prefetch-parallel : Parallel prefetches from fixed-size regions ** Benchmark Cycles Nanos 16-KiB parallel prefetcht0 0.50 0.23 16-KiB parallel prefetcht1 0.50 0.23 16-KiB parallel prefetcht2 0.50 0.23 16-KiB parallel prefetchnta 0.50 0.23 32-KiB parallel prefetcht0 0.50 0.23 32-KiB parallel prefetcht1 1.98 0.90 32-KiB parallel prefetcht2 1.99 0.91 32-KiB parallel prefetchnta 0.50 0.23 64-KiB parallel prefetcht0 2.00 0.91 64-KiB parallel prefetcht1 1.90 0.86 64-KiB parallel prefetcht2 2.00 0.91 64-KiB parallel prefetchnta 5.90 2.69 128-KiB parallel prefetcht0 2.26 1.03 128-KiB parallel prefetcht1 2.04 0.93 128-KiB parallel prefetcht2 2.04 0.93 128-KiB parallel prefetchnta 5.91 2.69 256-KiB parallel prefetcht0 3.66 1.67 256-KiB parallel prefetcht1 3.49 1.59 256-KiB parallel prefetcht2 3.49 1.59 256-KiB parallel prefetchnta 5.85 2.67 512-KiB parallel prefetcht0 5.25 2.39 512-KiB parallel prefetcht1 4.90 2.23 512-KiB parallel prefetcht2 4.90 2.24 512-KiB parallel prefetchnta 5.77 2.63 2048-KiB parallel prefetcht0 6.22 2.84 2048-KiB parallel prefetcht1 5.84 2.66 2048-KiB parallel prefetcht2 5.84 2.66 2048-KiB parallel prefetchnta 9.43 4.30 4096-KiB parallel prefetcht0 10.96 5.00 4096-KiB parallel prefetcht1 10.69 4.87 4096-KiB parallel prefetcht2 10.74 4.90 4096-KiB parallel prefetchnta 9.58 4.37 8192-KiB parallel prefetcht0 16.96 7.73 8192-KiB parallel prefetcht1 16.44 7.50 8192-KiB parallel prefetcht2 16.77 7.64 8192-KiB parallel prefetchnta 12.27 5.59 32768-KiB parallel prefetcht0 20.60 9.39 32768-KiB parallel prefetcht1 20.23 9.22 32768-KiB parallel prefetcht2 20.09 9.16 32768-KiB parallel prefetchnta 20.22 9.22 Finished in 4492 ms (memory/prefetch-parallel) ** Running group memory/pointer-chase : Pointer-chasing ** Benchmark Cycles Nanos Simple addressing chase, half diffpage 6.51 2.97 Simple addressing chase, different pages 8.49 3.87 Simple addressing chase with ALU op 6.01 2.74 load5 -> load4 -> alu 10.02 4.57 load4 -> load5 -> alu 11.03 5.03 8 parallel simple pointer chases 4.00 1.82 10 parallel complex pointer chases 5.16 2.35 10 parallel mixed pointer chases 5.19 2.37 Finished in 916 ms (memory/pointer-chase) ** Running group memory/load-serial : Serial loads from fixed-size regions ** Benchmark Cycles Nanos 16-KiB serial loads 4.00 1.82 24-KiB serial loads 4.00 1.82 30-KiB serial loads 4.00 1.82 31-KiB serial loads 4.00 1.82 32-KiB serial loads 4.01 1.83 33-KiB serial loads 6.02 2.74 34-KiB serial loads 8.01 3.65 35-KiB serial loads 9.81 4.47 40-KiB serial loads 11.93 5.44 48-KiB serial loads 11.96 5.45 56-KiB serial loads 11.95 5.45 64-KiB serial loads 12.12 5.52 80-KiB serial loads 11.98 5.46 96-KiB serial loads 11.98 5.46 112-KiB serial loads 12.01 5.48 128-KiB serial loads 12.00 5.47 196-KiB serial loads 15.10 6.88 252-KiB serial loads 21.27 9.70 256-KiB serial loads 21.11 9.63 260-KiB serial loads 20.99 9.57 384-KiB serial loads 28.64 13.06 512-KiB serial loads 31.71 14.46 1024-KiB serial loads 38.92 17.74 2048-KiB serial loads 47.21 21.52 Finished in 683 ms (memory/load-serial) ** Running group bmi : BMI false-dependency tests ** Benchmark Cycles Nanos dest-dependent tzcnt 3.00 1.37 dest-dependent lzcnt 3.00 1.37 dest-dependent popcnt 3.00 1.37 Finished in 190 ms (bmi) ** Running group studies/vzeroall : VZEROALL weirdness ** Benchmark Cycles Nanos vpaddq zmm0, zmm0, zmm0 Skipped because hardware doesn't support required features: [AVX512F] vpaddq zmm0, zmm1, zmm0 Skipped because hardware doesn't support required features: [AVX512F] vpaddq zmm0, zmm16, zmm0 Skipped because hardware doesn't support required features: [AVX512F] vpxor zmm16; vpaddq zmm0, zmm16, zmm0 Skipped because hardware doesn't support required features: [AVX512F] vpaddq ymm0, ymm0, ymm0 1.00 0.46 vpaddq ymm0, ymm1, ymm0 1.00 0.46 vpaddq xmm0, xmm0, xmm0 1.00 0.46 vpaddq xmm0, xmm1, xmm0 1.00 0.46 paddq xmm0, xmm0 1.00 0.46 paddq xmm0, xmm1 1.00 0.46 Finished in 97 ms (studies/vzeroall) Reverting no_turbo to 0 Succesfully restored no_turbo state: 0