Andres Freund <andres@anarazel.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.
regards, tom lane