Query:

SELECT name,
       "type",
       count(*),
       sum(total_bytes) total_bytes,
       sum(total_nblocks) total_nblocks,
       sum(free_bytes) free_bytes,
       sum(free_chunks) free_chunks,
       sum(used_bytes) used_bytes,
       sum(used_bytes) / sum(total_nblocks) AS hinky_chunk_size
FROM pg_backend_memory_contexts
WHERE path @> (SELECT path FROM pg_backend_memory_contexts WHERE name = 'CacheMemoryContext')
GROUP BY GROUPING SETS ((name, "type"), ());


Master

        name        |   type   | count | total_bytes | total_nblocks | free_bytes | free_chunks | used_bytes |   hinky_chunk_size    
--------------------+----------+-------+-------------+---------------+------------+-------------+------------+-----------------------
 CacheMemoryContext | AllocSet |     1 |     2097152 |             9 |     172904 |           1 |    1924248 |   213805.333333333333
 CachedPlan         | AllocSet |     3 |       32768 |            13 |      12712 |           2 |      20056 | 1542.7692307692307692
 CachedPlanQuery    | AllocSet |     4 |       36864 |            16 |      15072 |           1 |      21792 | 1362.0000000000000000
 CachedPlanSource   | AllocSet |     4 |       28672 |            14 |       9104 |           5 |      19568 | 1397.7142857142857143
 SPI Plan           | AllocSet |     2 |        2048 |             2 |       1200 |           0 |        848 |  424.0000000000000000
 SQL function       | AllocSet |     2 |        2048 |             2 |        976 |           0 |       1072 |  536.0000000000000000
 index info         | AllocSet |   138 |      287872 |           225 |     102272 |         118 |     185600 |  824.8888888888888889
 relation rules     | AllocSet |    88 |     2119680 |           516 |     303736 |          65 |    1815944 | 3519.2713178294573643
                    |          |   242 |     4607104 |           797 |     617976 |         192 |    3989128 | 5005.1794228356336261

(9 rows)

+0001-0003

         name         |   type   | count | total_bytes | total_nblocks | free_bytes | free_chunks | used_bytes |   hinky_chunk_size    
----------------------+----------+-------+-------------+---------------+------------+-------------+------------+-----------------------
 CacheMemoryContext   | AllocSet |     1 |     2097152 |             9 |     135952 |           1 |    1961200 |   217911.111111111111
 CachedPlan           | AllocSet |     3 |       32768 |            13 |      12712 |           2 |      20056 | 1542.7692307692307692
 CachedPlanQuery      | AllocSet |     4 |       36864 |            16 |      15072 |           1 |      21792 | 1362.0000000000000000
 CachedPlanSource     | AllocSet |     4 |       28672 |            14 |       9104 |           5 |      19568 | 1397.7142857142857143
 Relation shape cache | AllocSet |     1 |       16384 |             2 |       4616 |           2 |      11768 | 5884.0000000000000000
 SPI Plan             | AllocSet |     2 |        2048 |             2 |       1200 |           0 |        848 |  424.0000000000000000
 SQL function         | AllocSet |     2 |        2048 |             2 |        976 |           0 |       1072 |  536.0000000000000000
 index info           | AllocSet |   138 |      141312 |           138 |      90176 |           0 |      51136 |  370.5507246376811594
 relation rules       | AllocSet |    88 |     2119680 |           516 |     303736 |          65 |    1815944 | 3519.2713178294573643
                      |          |   243 |     4476928 |           712 |     573544 |          76 |    3903384 | 5482.2808988764044944
(10 rows)

+0004, 0005:

         name         |   type   | count | total_bytes | total_nblocks | free_bytes | free_chunks | used_bytes |   hinky_chunk_size    
----------------------+----------+-------+-------------+---------------+------------+-------------+------------+-----------------------
 CacheMemoryContext   | AllocSet |     1 |     2097152 |             9 |     135952 |           1 |    1961200 |   217911.111111111111
 CachedPlan           | AllocSet |     3 |       32768 |            13 |      12712 |           2 |      20056 | 1542.7692307692307692
 CachedPlanQuery      | AllocSet |     4 |       36864 |            16 |      15072 |           1 |      21792 | 1362.0000000000000000
 CachedPlanSource     | AllocSet |     4 |       28672 |            14 |       9104 |           5 |      19568 | 1397.7142857142857143
 Relation shape cache | AllocSet |     1 |       16384 |             2 |       4616 |           2 |      11768 | 5884.0000000000000000
 SPI Plan             | AllocSet |     2 |        2048 |             2 |       1200 |           0 |        848 |  424.0000000000000000
 SQL function         | AllocSet |     2 |        2048 |             2 |        976 |           0 |       1072 |  536.0000000000000000
 index info           | Proxy    |   138 |       45392 |           460 |          0 |           0 |      45392 |   98.6782608695652174
 relation rules       | AllocSet |    88 |     2119680 |           516 |     303736 |          65 |    1815944 | 3519.2713178294573643
                      |          |   243 |     4381008 |          1034 |     483368 |          76 |    3897640 | 3769.4777562862669246

(10 rows)