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Align benchmark::State to a cacheline. #1230

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merged 7 commits into from
Aug 16, 2024
Merged

Align benchmark::State to a cacheline. #1230

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f4ad6f5
Align benchmark::State to a cacheline.
ckennelly Sep 17, 2021
0b73e34
Merge branch 'main' into alignment
dmah42 Aug 16, 2024
06fdd92
Merge branch 'main' into alignment
dmah42 Aug 16, 2024
ac435c0
clang-format
dmah42 Aug 16, 2024
58f6937
remove redundant definitions
dmah42 Aug 16, 2024
8d60cfa
consolidate some of the defines
dmah42 Aug 16, 2024
d038342
separate cachline definition from alignment attribute macro
dmah42 Aug 16, 2024
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43 changes: 41 additions & 2 deletions include/benchmark/benchmark.h
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Original file line number Diff line number Diff line change
Expand Up @@ -290,11 +290,50 @@ BENCHMARK(BM_test)->Unit(benchmark::kMillisecond);
#define BENCHMARK_OVERRIDE
#endif

#if defined(__GNUC__)
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Not really sure if this outermost guard is needed, but then i don't know what set of per-cpu defines MSVC provides.

// Determine the cacheline size based on architecture
#if defined(__i386__) || defined(__x86_64__)
#define BENCHMARK_INTERNAL_CACHELINE_SIZE 64
#elif defined(__powerpc64__)
#define BENCHMARK_INTERNAL_CACHELINE_SIZE 128
#elif defined(__aarch64__)
#define BENCHMARK_INTERNAL_CACHELINE_SIZE 64
#elif defined(__arm__)
// Cache line sizes for ARM: These values are not strictly correct since
// cache line sizes depend on implementations, not architectures. There
// are even implementations with cache line sizes configurable at boot
// time.
#if defined(__ARM_ARCH_5T__)
#define BENCHMARK_INTERNAL_CACHELINE_SIZE 32
#elif defined(__ARM_ARCH_7A__)
#define BENCHMARK_INTERNAL_CACHELINE_SIZE 64
#endif // ARM_ARCH
#endif // arches
#endif // __GNUC__

#ifndef BENCHMARK_INTERNAL_CACHELINE_SIZE
// A reasonable default guess. Note that overestimates tend to waste more
// space, while underestimates tend to waste more time.
#define BENCHMARK_INTERNAL_CACHELINE_SIZE 64
#endif

#if defined(__GNUC__)
// Indicates that the declared object be cache aligned using
// `BENCHMARK_INTERNAL_CACHELINE_SIZE` (see above).
#define BENCHMARK_INTERNAL_CACHELINE_ALIGNED \
__attribute__((aligned(BENCHMARK_INTERNAL_CACHELINE_SIZE)))
#elif defined(_MSC_VER)
#define BENCHMARK_INTERNAL_CACHELINE_ALIGNED \
__declspec(align(BENCHMARK_INTERNAL_CACHELINE_SIZE))
#else
#define BENCHMARK_INTERNAL_CACHELINE_ALIGNED
#endif

#if defined(_MSC_VER)
#pragma warning(push)
// C4251: <symbol> needs to have dll-interface to be used by clients of class
#pragma warning(disable : 4251)
#endif
#endif // _MSC_VER_

namespace benchmark {
class BenchmarkReporter;
Expand Down Expand Up @@ -759,7 +798,7 @@ enum Skipped

// State is passed to a running Benchmark and contains state for the
// benchmark to use.
class BENCHMARK_EXPORT State {
class BENCHMARK_EXPORT BENCHMARK_INTERNAL_CACHELINE_ALIGNED State {
public:
struct StateIterator;
friend struct StateIterator;
Expand Down