From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Active zombies at AIX |
Date: | 2017-02-06 21:22:51 |
Message-ID: | 20170206212251.ha6reift2zapuf3i@alap3.anarazel.de |
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Lists: | pgsql-hackers |
On 2017-02-06 16:06:25 -0500, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2017-02-06 15:39:10 -0500, Peter Eisentraut wrote:
> >> On 2/6/17 6:28 AM, Konstantin Knizhnik wrote:
> >>> I wonder why do we prohibit now configuration of Postgres without mmap?
>
> >> It's not really prohibited, but it's not something that people generally
> >> need, and we want to keep the number of configuration variations low.
>
> > I think that was a fairly bad call. Making it hard to use anything but
> > mmap (on mmap supporting platforms) caused a fair bit of trouble and
> > performance regressions on several platforms by now (freebsd reported it
> > fairly quickly, and now aix), all to avoid a trivial amount of code and
> > one guc.
>
> > FWIW, there's a patch somewhere in the archive making it configurable.
>
> Clearly we should do something, but I'm not sure that a GUC is the right
> answer; far too few people would set it correctly. I think it might be
> better to have the per-platform "template" files decide whether to set
> USE_ANONYMOUS_SHMEM or not.
Well, sysv shmem will be less "comfortable" to use on those platforms
too. And you'll usually only hit the performance problems on bigger
installations. I don't think it'll be an improvement if after an upgrade
postgres doesn't work anymore because people have gotten used to not
having to configure sys shmem.
I suspect a better solution would be to have a list GUC with a platform
dependant default (i.e. sysv, anonymous on freebsd/aix; the other way
round on linux). At startup we'd then try those in order.
Regards,
Andres
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