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Update yield logic for ARM processor #1325

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merged 3 commits into from
Apr 12, 2022
Merged

Update yield logic for ARM processor #1325

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a689855
fix yield on ARM
lalitb Apr 12, 2022
5afaf3a
fix benchmark test
lalitb Apr 12, 2022
1be1b7b
Merge branch 'main' into arm-yield
lalitb Apr 12, 2022
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4 changes: 1 addition & 3 deletions api/include/opentelemetry/common/spin_lock_mutex.h
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Original file line number Diff line number Diff line change
Expand Up @@ -101,9 +101,7 @@ class SpinLockMutex
__builtin_ia32_pause();
# endif
#elif defined(__arm__)
// This intrinsic should fail to be found if YIELD is not supported on the current
// processor.
__yield();
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Is there a way (e.g. macro or something) to determine if __yield is available?

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Curious where this pattern comes from.

BTW, do we need add CI for arm?

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@lalitb lalitb Apr 12, 2022 •
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Is there a way (e.g. macro or something) to determine if __yield is available?

There is no standard approach to do this. ARM vendors may choose not to implement these extensions.

Curious where this pattern comes from.

This patten of yielding ? It was written by Josh. I would prefer to let these platform specific code go away as long term solution, and rely on yield provided by standard C++ library.

BTW, do we need add CI for arm?

Yes we need it. @esigo has done some initial work #1165, but seems builds are very slow, as there is no ARM virtual machines provided by github.

__asm__ volatile("yield" ::: "memory");
#else
// TODO: Issue PAGE/YIELD on other architectures.
#endif
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2 changes: 1 addition & 1 deletion api/test/common/spinlock_benchmark.cc
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Expand Up @@ -93,7 +93,7 @@ static void BM_ProcYieldSpinLockThrashing(benchmark::State &s)
__builtin_ia32_pause();
# endif
#elif defined(__arm__)
__yield();
__asm__ volatile("yield" ::: "memory");
#endif
}
},
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