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perf(native): Fix incorrect initialization of empty 'folly::Promise' #26313
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perf(native): Fix incorrect initialization of empty 'folly::Promise' #26313
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This is followup for prestodb#26094 For an empty `folly::Promise` object that is expected to be overwritten, we should use `folly::makeEmpty()` to initialize it (it is 'invalid') instead of the default constructor (it will be 'valid' but 'not fulfilled', assigning to it will cause an exception. Creating an exception triggers a stack unwind, which can saturate the CPU in high-concurrency scenarios, **causing significant performance issues**.
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PingLiuPing
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Thanks.
@amitkdutta Could you help review and merge this PR?
amitkdutta
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Looks great.
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This is another follow-up for #26094
For an empty
folly::Promiseobject that is expected to be overwritten,we should use
folly::makeEmpty()to initialize it (it is 'invalid')instead of the default constructor (it will be 'valid' but
'not fulfilled', assigning to it will cause an exception. Creating an
exception triggers a stack unwind, which can saturate the CPU in
high-concurrency scenarios, causing significant performance issues.