From 8cc139bec34a2971b0682a04eb52ce7b3f5bb425 Mon Sep 17 00:00:00 2001 From: Tomas Vondra Date: Mon, 7 Apr 2025 22:54:49 +0200 Subject: Introduce pg_shmem_allocations_numa view Introduce new pg_shmem_alloctions_numa view with information about how shared memory is distributed across NUMA nodes. For each shared memory segment, the view returns one row for each NUMA node backing it, with the total amount of memory allocated from that node. The view may be relatively expensive, especially when executed for the first time in a backend, as it has to touch all memory pages to get reliable information about the NUMA node. This may also force allocation of the shared memory. Unlike pg_shmem_allocations, the view does not show anonymous shared memory allocations. It also does not show memory allocated using the dynamic shared memory infrastructure. Author: Jakub Wartak Reviewed-by: Andres Freund Reviewed-by: Bertrand Drouvot Reviewed-by: Tomas Vondra Discussion: https://postgr.es/m/CAKZiRmxh6KWo0aqRqvmcoaX2jUxZYb4kGp3N%3Dq1w%2BDiH-696Xw%40mail.gmail.com --- doc/src/sgml/system-views.sgml | 95 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) (limited to 'doc/src') diff --git a/doc/src/sgml/system-views.sgml b/doc/src/sgml/system-views.sgml index 4f336ee0adf..0eba37268bf 100644 --- a/doc/src/sgml/system-views.sgml +++ b/doc/src/sgml/system-views.sgml @@ -181,6 +181,11 @@ shared memory allocations + + pg_shmem_allocations_numa + NUMA node mappings for shared memory allocations + + pg_stats planner statistics @@ -4051,6 +4056,96 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx + + <structname>pg_shmem_allocations_numa</structname> + + + pg_shmem_allocations_numa + + + + The pg_shmem_allocations_numa shows how shared + memory allocations in the server's main shared memory segment are distributed + across NUMA nodes. This includes both memory allocated by + PostgreSQL itself and memory allocated + by extensions using the mechanisms detailed in + . This view will output multiple rows + for each of the shared memory segments provided that they are spread accross + multiple NUMA nodes. This view should not be queried by monitoring systems + as it is very slow and may end up allocating shared memory in case it was not + used earlier. + Current limitation for this view is that won't show anonymous shared memory + allocations. + + + + Note that this view does not include memory allocated using the dynamic + shared memory infrastructure. + + + + + When determining the NUMA node, the view touches + all memory pages for the shared memory segment. This will force + allocation of the shared memory, if it wasn't allocated already, + and the memory may get allocated in a single NUMA + node (depending on system configuration). + + + + + <structname>pg_shmem_allocations_numa</structname> Columns + + + + + Column Type + + + Description + + + + + + + + name text + + + The name of the shared memory allocation. + + + + + + numa_node int4 + + + ID of NUMA node + + + + + + size int4 + + + Size of the allocation on this particular NUMA memory node in bytes + + + + + +
+ + + By default, the pg_shmem_allocations_numa view can be + read only by superusers or roles with privileges of the + pg_read_all_stats role. + + + <structname>pg_stats</structname> -- cgit v1.2.3