On Tue, Jun 6, 2017 at 10:14 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Robert Haas <robertmh...@gmail.com> writes:
>> I think the idea of retrying process creation (and I definitely agree
>> with Tom and Magnus that we have to retry process creation, not just
>> individual mappings) is a good place to start.  Now if we find that we
>> are having to retry frequently, then I think we might need to try
>> something along the lines of what Andres proposed and what nginx
>> apparently did.  However, any fixed address will be prone to
>> occasional failures (or maybe, on some systems, regular failures) if
>> that particular address happens to get claimed by something.  I don't
>> think we can say that there is any address where that definitely won't
>> happen.  So I would say let's do this retry thing first, and then if
>> that proves inadequate, we can also try moving the mappings to a range
>> where conflicts are less likely.
> By definition, the address range we're trying to reuse worked successfully
> in the postmaster process.  I don't see how forcing a specific address
> could do anything but create an additional risk of postmaster startup
> failure.

I think it won't create an additional risk, because the idea is that
if we fail to map the shm segment at a predefined address, then we
will allow the system to choose the initial address as we are doing
now.  So, it can reduce chances of doing retries.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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