| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Sean Chittenden <sean(at)chittenden(dot)org> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PATCH] PostgreSQL 9.4 mmap(2) performance regression on FreeBSD... |
| Date: | 2014-10-13 15:01:27 |
| Message-ID: | 477.1413212487@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Sean Chittenden <sean(at)chittenden(dot)org> writes:
> In the same breath, it would also be nice if the following were committed:
> [ use named POSIX semaphores on FreeBSD ]
Really? Why? According to the notes in our code, named POSIX semaphores
are the least attractive of the three Unixoid semaphore APIs we support,
because they require eating a file descriptor per backend per
max_connection slot. That's a lot of FDs in any large configuration.
FreeBSD's support for SysV semaphores would have to be pretty darn awful
to make me think this was a good change, and I've not heard complaints
in that direction before.
If you meant to propose using *unnamed* POSIX semaphores, that might be
a reasonable change, but it would still need some supporting evidence.
regards, tom lane
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