Avoid calling clock::now in the common case. #1862
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Summary: Avoid calling clock::now in the common case. Clock::now() can be an expensive call (a call to libc's __clock_gettime). PGO data shows that the first check almost always succeeds, which makes the call to Clock::now redundant. This patch peels one iteration that calls f() before calling clock::now(). Notice that a very common use of this API is a function that performs a single load in the function, so timing is not a major concern. Differential Revision: D39611860 fbshipit-source-id: 105ce07995bdc96627aa8b3011dc565645a498c6
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This pull request was exported from Phabricator. Differential Revision: D39611860 |
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Summary: X-link: facebook/folly#1862 Avoid calling clock::now in the common case. Clock::now() can be an expensive call (a call to libc's __clock_gettime). PGO data shows that the first check almost always succeeds, which makes the call to Clock::now redundant. This patch peels one iteration that calls f() before calling clock::now(). Notice that a very common use of this API is a function that performs a single load in the function, so timing is not a major concern. Reviewed By: magedm Differential Revision: D39611860 fbshipit-source-id: 8c7affc83f1e86fe3c8b2401391e1159d08a99ec
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Summary:
Avoid calling clock::now in the common case.
Clock::now() can be an expensive call (a call to libc's __clock_gettime). PGO
data shows that the first check almost always succeeds, which makes the call to
Clock::now redundant. This patch peels one iteration that calls f() before
calling clock::now(). Notice that a very common use of this API is a function
that performs a single load in the function, so timing is not a major concern.
Differential Revision: D39611860