PostgreSQL performance scaling

David Xu davidxu at
Tue Nov 23 02:34:59 UTC 2010

Ivan Voras wrote:
> On 23 November 2010 10:35, David Xu <davidxu at> wrote:
>> Ivan Voras wrote:
>>> and the overall behaviour is similar - the processes spend a lot of time
>>> in "sbwait" and "ksem" states.
>> Strange, the POSIX semaphore in head branch does not use ksem, it is
>> based on umtx, there is no limit on POSIX semaphore, the only limit
>> is process's address space which limits how many semaphores can be
>> used.
> *shrug*; I don't know how it could be wrong - this PostgreSQL was
> built from ports after I upgraded & booted 9-current.
> If it didn't use POSIX semaphores from HEAD, shared semaphores
> wouldn't have worked, right?

It may work, but even it is shared in memory, it still enters
kernel to do P/V operation.

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