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posix_sema.c
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Thomas Munro authored
In a USE_UNNAMED_SEMAPHORES build, the default on Linux and FreeBSD since commit ecb0d20a, we have an array of sem_t objects. This turned out to reduce performance compared to the previous default USE_SYSV_SEMAPHORES on an 8 socket system. Testing showed that the lost performance could be regained by padding the array elements so that they have their own cache lines. This matches what we do for similar hot arrays (see LWLockPadded, WALInsertLockPadded). Back-patch to 10, where unnamed semaphores were adopted as the default semaphore interface on those operating systems. Author: Thomas Munro Reviewed-by: Andres Freund Reported-by: Mithun Cy Tested-by: Mithun Cy, Tom Lane, Thomas Munro Discussion: https://postgr.es/m/CAD__OugYDM3O%2BdyZnnZSbJprSfsGFJcQ1R%3De59T3hcLmDug4_w%40mail.gmail.com
Thomas Munro authoredIn a USE_UNNAMED_SEMAPHORES build, the default on Linux and FreeBSD since commit ecb0d20a, we have an array of sem_t objects. This turned out to reduce performance compared to the previous default USE_SYSV_SEMAPHORES on an 8 socket system. Testing showed that the lost performance could be regained by padding the array elements so that they have their own cache lines. This matches what we do for similar hot arrays (see LWLockPadded, WALInsertLockPadded). Back-patch to 10, where unnamed semaphores were adopted as the default semaphore interface on those operating systems. Author: Thomas Munro Reviewed-by: Andres Freund Reported-by: Mithun Cy Tested-by: Mithun Cy, Tom Lane, Thomas Munro Discussion: https://postgr.es/m/CAD__OugYDM3O%2BdyZnnZSbJprSfsGFJcQ1R%3De59T3hcLmDug4_w%40mail.gmail.com
