| From: | Sean Chittenden <sean(at)chittenden(dot)org> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| 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: | 2014-10-14 05:28:16 |
| Message-ID: | sig.0364cdbb18.8309646D-CD50-46AB-926E-73E88FAA5945@chittenden.org |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
> Really? Why?
Because it was found to be lighter weight. See §5 (bottom of ppg 8).
https://kib.kiev.ua/kib/pgsql_perf.pdf
> 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.
https://lists.freebsd.org/pipermail/svn-src-stable-10/2014-October/003515.html
-sc
--
Sean Chittenden
sean(at)chittenden(dot)org
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Amit Kapila | 2014-10-14 06:04:23 | Re: Wait free LW_SHARED acquisition - v0.9 |
| Previous Message | Ali Akbar | 2014-10-14 04:37:01 | Re: Function array_agg(array) |