Re: Is there a significant difference in Memory settings between 9.5and 12

Tory M Blue <tmblue@gmail.com> writes:
> 12 will not start at 10GB, even though it's the same hardware, same config
> file, same physical box, same everything, just version 12 vs 9.5

For me, using all-default settings (in particular, shared_buffers =
128MB), the shared memory block is about 141.6MB using 9.5 and 142.1MB
using 12.  So there's half a meg or so of additional data in v12, but
certainly not gigabytes worth.

Are you trying to start both postmasters concurrently?  Maybe you're
hitting some kernel limit on the total amount of shared memory in the
system.

                        regards, tom lane

shared_memory_type (enum)

Specifies the shared memory implementation that the server should use for the main shared memory region that holds PostgreSQL's shared buffers and other shared data. Possible values are mmap (for anonymous shared memory allocated using mmap), sysv (for System V shared memory allocated via shmget) and windows (for Windows shared memory). Not all values are supported on all platforms; the first supported option is the default for that platform. The use of the sysv option, which is not the default on any platform, is generally discouraged because it typically requires non-default kernel settings to allow for large allocations (see Section 18.4.1).