You can check the cache hit ratio and size of the GMC area in the system view pgx_stat_gmc. Refer to "D.6 pgx_stat_gmc" for information on the columns.
If the cache hit ratio is low and the current memory usage is close to pgx_global_metacache, increase the pgx_global_metacache setting because performance may be degraded.
Refer to "9.6 Monitoring Database Activity" in the Operations Guide for information on the statistics.