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a357259bf8
This patch adds some more directives to the benchmark inputs file, moving functionality from the Makefile and making the code generation script a bit cleaner. The function argument and return types that were earlier added as variables in the makefile and passed to the script via command line arguments are now the 'args' and 'ret' directive respectively. 'args' should be a colon separated list of argument types (skipped if the function doesn't accept any arguments) and 'ret' should be the return type. Additionally, an 'includes' directive may have a comma separated list of headers to include in the source. For example, the pow input file now looks like this: 42.0, 42.0 1.0000000000000020, 1.5 I did this to unclutter the benchtests Makefile a bit and eventually eliminate dependency of the tests on the Makefile and have tests depend on their respective include files only.
91 lines
3.6 KiB
Plaintext
91 lines
3.6 KiB
Plaintext
Using the glibc microbenchmark suite
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====================================
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The glibc microbenchmark suite automatically generates code for specified
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functions, builds and calls them repeatedly for given inputs to give some
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basic performance properties of the function.
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Running the benchmark:
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=====================
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The benchmark can be executed by invoking make as follows:
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$ make bench
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This runs each function for 10 seconds and appends its output to
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benchtests/bench.out. To ensure that the tests are rebuilt, one could run:
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$ make bench-clean
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The duration of each test can be configured setting the BENCH_DURATION variable
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in the call to make. One should run `make bench-clean' before changing
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BENCH_DURATION.
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$ make BENCH_DURATION=1 bench
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The benchmark suite does function call measurements using architecture-specific
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high precision timing instructions whenever available. When such support is
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not available, it uses clock_gettime (CLOCK_PROCESS_CPUTIME_ID). One can force
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the benchmark to use clock_gettime by invoking make as follows:
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$ make USE_CLOCK_GETTIME=1 bench
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Again, one must run `make bench-clean' before changing the measurement method.
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Adding a function to benchtests:
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===============================
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If the name of the function is `foo', then the following procedure should allow
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one to add `foo' to the bench tests:
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- Append the function name to the bench variable in the Makefile.
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- Make a file called `foo-inputs` to provide the definition and input for the
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function. The file should have some directives telling the parser script
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about the function and then one input per line. Directives are lines that
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have a special meaning for the parser and they begin with two hashes '##'.
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The following directives are recognized:
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- args: This should be assigned a colon separated list of types of the input
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arguments. This directive may be skipped if the function does not take any
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inputs.
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- ret: This should be assigned the type that the function returns. This
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directive may be skipped if the function does not return a value.
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- includes: This should be assigned a comma separated list of headers that
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need to be included to provide declarations for the function and types it
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may need.
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- name: See following section for instructions on how to use this directive.
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Lines beginning with a single hash '#' are treated as comments. See
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pow-inputs for an example of an input file.
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Multiple execution units per function:
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=====================================
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Some functions have distinct performance characteristics for different input
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domains and it may be necessary to measure those separately. For example, some
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math functions perform computations at different levels of precision (64-bit vs
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240-bit vs 768-bit) and mixing them does not give a very useful picture of the
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performance of these functions. One could separate inputs for these domains in
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the same file by using the `name' directive that looks something like this:
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##name: 240bit
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See the pow-inputs file for an example of what such a partitioned input file
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would look like.
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Benchmark Sets:
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==============
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In addition to standard benchmarking of functions, one may also generate
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custom outputs for a set of functions. This is currently used by string
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function benchmarks where the aim is to compare performance between
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implementations at various alignments and for various sizes.
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To add a benchset for `foo':
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- Add `foo' to the benchset variable.
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- Write your bench-foo.c that prints out the measurements to stdout.
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- On execution, a bench-foo.out is created in $(objpfx) with the contents of
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stdout.
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