pg_shmem_allocations
   The pg_shmem_allocations view shows allocations
   made from the server's main shared memory segment.  This includes both
   memory allocated by postgres itself and memory
   allocated by extensions using the mechanisms detailed in
   Section 38.10.10.
  
Note that this view does not include memory allocated using the dynamic shared memory infrastructure.
Table 52.89. pg_shmem_allocations Columns
| Column Type Description | 
|---|
| 
        
       The name of the shared memory allocation. NULL for unused memory
       and  | 
| 
        The offset at which the allocation starts. NULL for anonymous allocations, since details related to them are not known. | 
| 
        Size of the allocation | 
| 
        
       Size of the allocation including padding. For anonymous
       allocations, no information about padding is available, so the
        | 
   Anonymous allocations are allocations that have been made
   with ShmemAlloc() directly, rather than via
   ShmemInitStruct() or
   ShmemInitHash().
  
   By default, the pg_shmem_allocations view can be
   read only by superusers.