Andres Freund <> 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

                        regards, tom lane

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