From 6fe26ca004ada3a9a6decc90ecfada44b058e94d Mon Sep 17 00:00:00 2001 From: Jakub Wartak Date: Wed, 19 Mar 2025 09:34:56 +0100 Subject: [PATCH v19 6/8] Add pg_buffercache_numa view with NUMA node info Introduces a new view pg_buffercache_numa, showing a NUMA memory node for each individual buffer. To determine the NUMA node for a buffer, we first need to touch the memory pages using pg_numa_touch_mem_if_required, otherwise we might get status -2 (ENOENT = The page is not present), indicating the page is either unmapped or unallocated. The size of a database block and OS memory page may differ. For example the default block size (BLCKSZ) sis 8KB, while the memory page is 4KB, but it's also possible to make the block size smaller (e.g. 1KB). It's enough to query the NUMA node only once per memory page, we don't need to repeat this for every buffer. review: What if we get multiple pages per buffer (the default). Could we get multiple nodes per buffer? 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 --- contrib/pg_buffercache/Makefile | 3 +- .../expected/pg_buffercache_numa.out | 28 +++ .../expected/pg_buffercache_numa_1.out | 3 + contrib/pg_buffercache/meson.build | 2 + .../pg_buffercache--1.5--1.6.sql | 39 ++++ contrib/pg_buffercache/pg_buffercache.control | 2 +- contrib/pg_buffercache/pg_buffercache_pages.c | 180 +++++++++++++++++- .../sql/pg_buffercache_numa.sql | 20 ++ doc/src/sgml/pgbuffercache.sgml | 61 +++++- 9 files changed, 328 insertions(+), 10 deletions(-) create mode 100644 contrib/pg_buffercache/expected/pg_buffercache_numa.out create mode 100644 contrib/pg_buffercache/expected/pg_buffercache_numa_1.out create mode 100644 contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql create mode 100644 contrib/pg_buffercache/sql/pg_buffercache_numa.sql diff --git a/contrib/pg_buffercache/Makefile b/contrib/pg_buffercache/Makefile index eae65ead9e5..2a33602537e 100644 --- a/contrib/pg_buffercache/Makefile +++ b/contrib/pg_buffercache/Makefile @@ -8,7 +8,8 @@ OBJS = \ EXTENSION = pg_buffercache DATA = pg_buffercache--1.2.sql pg_buffercache--1.2--1.3.sql \ pg_buffercache--1.1--1.2.sql pg_buffercache--1.0--1.1.sql \ - pg_buffercache--1.3--1.4.sql pg_buffercache--1.4--1.5.sql + pg_buffercache--1.3--1.4.sql pg_buffercache--1.4--1.5.sql \ + pg_buffercache--1.5--1.6.sql PGFILEDESC = "pg_buffercache - monitoring of shared buffer cache in real-time" REGRESS = pg_buffercache diff --git a/contrib/pg_buffercache/expected/pg_buffercache_numa.out b/contrib/pg_buffercache/expected/pg_buffercache_numa.out new file mode 100644 index 00000000000..d4de5ea52fc --- /dev/null +++ b/contrib/pg_buffercache/expected/pg_buffercache_numa.out @@ -0,0 +1,28 @@ +SELECT NOT(pg_numa_available()) AS skip_test \gset +\if :skip_test +\quit +\endif +select count(*) = (select setting::bigint + from pg_settings + where name = 'shared_buffers') +from pg_buffercache_numa; + ?column? +---------- + t +(1 row) + +-- Check that the functions / views can't be accessed by default. To avoid +-- having to create a dedicated user, use the pg_database_owner pseudo-role. +SET ROLE pg_database_owner; +SELECT count(*) > 0 FROM pg_buffercache_numa; +ERROR: permission denied for view pg_buffercache_numa +RESET role; +-- Check that pg_monitor is allowed to query view / function +SET ROLE pg_monitor; +SELECT count(*) > 0 FROM pg_buffercache_numa; + ?column? +---------- + t +(1 row) + +RESET role; diff --git a/contrib/pg_buffercache/expected/pg_buffercache_numa_1.out b/contrib/pg_buffercache/expected/pg_buffercache_numa_1.out new file mode 100644 index 00000000000..6dd6824b4e4 --- /dev/null +++ b/contrib/pg_buffercache/expected/pg_buffercache_numa_1.out @@ -0,0 +1,3 @@ +SELECT NOT(pg_numa_available()) AS skip_test \gset +\if :skip_test +\quit diff --git a/contrib/pg_buffercache/meson.build b/contrib/pg_buffercache/meson.build index 12d1fe48717..7cd039a1df9 100644 --- a/contrib/pg_buffercache/meson.build +++ b/contrib/pg_buffercache/meson.build @@ -23,6 +23,7 @@ install_data( 'pg_buffercache--1.2.sql', 'pg_buffercache--1.3--1.4.sql', 'pg_buffercache--1.4--1.5.sql', + 'pg_buffercache--1.5--1.6.sql', 'pg_buffercache.control', kwargs: contrib_data_args, ) @@ -34,6 +35,7 @@ tests += { 'regress': { 'sql': [ 'pg_buffercache', + 'pg_buffercache_numa', ], }, } diff --git a/contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql b/contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql new file mode 100644 index 00000000000..720dc84b2c9 --- /dev/null +++ b/contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql @@ -0,0 +1,39 @@ +/* contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql */ + +-- complain if script is sourced in psql, rather than via CREATE EXTENSION +\echo Use "CREATE EXTENSION pg_buffercache" to load this file. \quit + +-- Register the new functions. +CREATE OR REPLACE FUNCTION pg_buffercache_pages() +RETURNS SETOF RECORD +AS 'MODULE_PATHNAME', 'pg_buffercache_pages' +LANGUAGE C PARALLEL SAFE; + +CREATE OR REPLACE FUNCTION pg_buffercache_numa_pages() +RETURNS SETOF RECORD +AS 'MODULE_PATHNAME', 'pg_buffercache_numa_pages' +LANGUAGE C PARALLEL SAFE; + +-- Create a view for convenient access. +CREATE OR REPLACE VIEW pg_buffercache AS + SELECT P.* FROM pg_buffercache_pages() AS P + (bufferid integer, relfilenode oid, reltablespace oid, reldatabase oid, + relforknumber int2, relblocknumber int8, isdirty bool, usagecount int2, + pinning_backends int4); + +CREATE OR REPLACE VIEW pg_buffercache_numa AS + SELECT P.* FROM pg_buffercache_numa_pages() AS P + (bufferid integer, relfilenode oid, reltablespace oid, reldatabase oid, + relforknumber int2, relblocknumber int8, isdirty bool, usagecount int2, + pinning_backends int4, node_id int4); + +-- Don't want these to be available to public. +REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC; +REVOKE ALL ON FUNCTION pg_buffercache_numa_pages() FROM PUBLIC; +REVOKE ALL ON pg_buffercache FROM PUBLIC; +REVOKE ALL ON pg_buffercache_numa FROM PUBLIC; + +GRANT EXECUTE ON FUNCTION pg_buffercache_pages() TO pg_monitor; +GRANT EXECUTE ON FUNCTION pg_buffercache_numa_pages() TO pg_monitor; +GRANT SELECT ON pg_buffercache TO pg_monitor; +GRANT SELECT ON pg_buffercache_numa TO pg_monitor; diff --git a/contrib/pg_buffercache/pg_buffercache.control b/contrib/pg_buffercache/pg_buffercache.control index 5ee875f77dd..b030ba3a6fa 100644 --- a/contrib/pg_buffercache/pg_buffercache.control +++ b/contrib/pg_buffercache/pg_buffercache.control @@ -1,5 +1,5 @@ # pg_buffercache extension comment = 'examine the shared buffer cache' -default_version = '1.5' +default_version = '1.6' module_pathname = '$libdir/pg_buffercache' relocatable = true diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c index d65b3bdf8df..535123aef1c 100644 --- a/contrib/pg_buffercache/pg_buffercache_pages.c +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -11,12 +11,13 @@ #include "access/htup_details.h" #include "catalog/pg_type.h" #include "funcapi.h" +#include "port/pg_numa.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" #define NUM_BUFFERCACHE_PAGES_MIN_ELEM 8 -#define NUM_BUFFERCACHE_PAGES_ELEM 9 +#define NUM_BUFFERCACHE_PAGES_ELEM 10 #define NUM_BUFFERCACHE_SUMMARY_ELEM 5 #define NUM_BUFFERCACHE_USAGE_COUNTS_ELEM 4 @@ -46,6 +47,7 @@ typedef struct * because of bufmgr.c's PrivateRefCount infrastructure. */ int32 pinning_backends; + int32 numa_node_id; } BufferCachePagesRec; @@ -64,15 +66,59 @@ typedef struct * relation node/tablespace/database/blocknum and dirty indicator. */ PG_FUNCTION_INFO_V1(pg_buffercache_pages); +PG_FUNCTION_INFO_V1(pg_buffercache_numa_pages); PG_FUNCTION_INFO_V1(pg_buffercache_summary); PG_FUNCTION_INFO_V1(pg_buffercache_usage_counts); PG_FUNCTION_INFO_V1(pg_buffercache_evict); +/* Only need to touch memory once per backend process lifetime */ +static bool firstNumaTouch = true; + /* - * Helper routine for pg_buffercache_pages(). + * Helper routine to map Buffers into addresses that is used by + * pg_numa_query_pages(). + * + * When database block size (BLCKSZ) is smaller than the OS page size (4kB), + * multiple database buffers will map to the same OS memory page. In this case, + * we only need to query the NUMA node for the first memory address of each + * unique OS page rather than for every buffer. * - * review: maybe describe what the helper does? Also, I guess we don't want to - * keep updating this whenever someone else uses the helper, right? + * In order to get reliable results we also need to touch memory pages, so that + * inquiry about NUMA memory node doesn't return -2 (which indicates + * unmapped/unallocated pages). + */ +static inline void +pg_buffercache_numa_prepare_ptrs(int buffer_id, float pages_per_blk, + Size os_page_size, + void **os_page_ptrs) +{ + size_t blk2page = (size_t) (buffer_id * pages_per_blk); + + for (size_t j = 0; j < pages_per_blk; j++) + { + size_t blk2pageoff = blk2page + j; + + if (os_page_ptrs[blk2pageoff] == 0) + { + volatile uint64 touch pg_attribute_unused(); + + /* NBuffers starts from 1 */ + os_page_ptrs[blk2pageoff] = (char *) BufferGetBlock(buffer_id + 1) + + (os_page_size * j); + + /* Only need to touch memory once per backend process lifetime */ + if (firstNumaTouch) + pg_numa_touch_mem_if_required(touch, os_page_ptrs[blk2pageoff]); + + } + + CHECK_FOR_INTERRUPTS(); + } +} + +/* + * Helper routine for pg_buffercache_pages() and pg_buffercache_numa_pages(). +>>>>>>> 704ed2dd2cb (Extend pg_buffercache with new view pg_buffercache_numa to show NUMA memory node for individual buffer.) */ static BufferCachePagesContext * pg_buffercache_init_entries(FuncCallContext *funcctx, FunctionCallInfo fcinfo) @@ -122,9 +168,12 @@ pg_buffercache_init_entries(FuncCallContext *funcctx, FunctionCallInfo fcinfo) TupleDescInitEntry(tupledesc, (AttrNumber) 8, "usage_count", INT2OID, -1, 0); - if (expected_tupledesc->natts == NUM_BUFFERCACHE_PAGES_ELEM) + if (expected_tupledesc->natts >= NUM_BUFFERCACHE_PAGES_ELEM - 1) TupleDescInitEntry(tupledesc, (AttrNumber) 9, "pinning_backends", INT4OID, -1, 0); + if (expected_tupledesc->natts == NUM_BUFFERCACHE_PAGES_ELEM) + TupleDescInitEntry(tupledesc, (AttrNumber) 10, "node_id", + INT4OID, -1, 0); fctx->tupdesc = BlessTupleDesc(tupledesc); @@ -143,7 +192,7 @@ pg_buffercache_init_entries(FuncCallContext *funcctx, FunctionCallInfo fcinfo) } /* - * Helper routine for pg_buffercache_pages(). + * Helper routine for pg_buffercache_pages() and pg_buffercache_numa_pages(). * * Save buffer cache information for a single buffer. */ @@ -178,11 +227,13 @@ pg_buffercache_save_tuple(int record_id, BufferCachePagesContext *fctx) else bufRecord->isvalid = false; + bufRecord->numa_node_id = -1; + UnlockBufHdr(bufHdr, buf_state); } /* - * Helper routine for pg_buffercache_pages(). + * Helper routine for pg_buffercache_pages() and pg_buffercache_numa_pages(). * * Format and return a tuple for a single buffer cache entry. */ @@ -218,6 +269,7 @@ get_buffercache_tuple(int record_id, BufferCachePagesContext *fctx) * unused for v1.0 callers, but the array is always long enough */ values[8] = Int32GetDatum(bufRecord->pinning_backends); + values[9] = Int32GetDatum(bufRecord->numa_node_id); } /* Build and return the tuple. */ @@ -267,6 +319,120 @@ pg_buffercache_pages(PG_FUNCTION_ARGS) SRF_RETURN_DONE(funcctx); } +/* + * This is almost identical to the above, but performs + * NUMA inuqiry about memory mappings. + */ +Datum +pg_buffercache_numa_pages(PG_FUNCTION_ARGS) +{ + FuncCallContext *funcctx; + BufferCachePagesContext *fctx; /* User function context. */ + + if (SRF_IS_FIRSTCALL()) + { + int i; + Size os_page_size = 0; + void **os_page_ptrs = NULL; + int *os_pages_status = NULL; + uint64 os_page_count = 0; + float pages_per_blk = 0; + + funcctx = SRF_FIRSTCALL_INIT(); + + if (pg_numa_init() == -1) + elog(ERROR, "libnuma initialization failed or NUMA is not supported on this platform"); + + fctx = pg_buffercache_init_entries(funcctx, fcinfo); + + /* + * Different database block sizes (4kB, 8kB, ..., 32kB) can be used, + * while the OS may have different memory page sizes. + * + * To correctly map between them, we need to: 1. Determine the OS + * memory page size 2. Calculate how many OS pages are used by all + * buffer blocks 3. Calculate how many OS pages are contained within + * each database block. + * + * This information is needed before calling move_pages() for NUMA + * node id inquiry. + */ + os_page_size = pg_numa_get_pagesize(); + os_page_count = ((uint64) NBuffers * BLCKSZ) / os_page_size; + pages_per_blk = (float) BLCKSZ / os_page_size; + + elog(DEBUG1, "NUMA: os_page_count=%lu os_page_size=%zu pages_per_blk=%.2f", + (unsigned long) os_page_count, os_page_size, pages_per_blk); + + os_page_ptrs = palloc0(sizeof(void *) * os_page_count); + os_pages_status = palloc(sizeof(uint64) * os_page_count); + + /* + * If we ever get 0xff back from kernel inquiry, then we probably have + * bug in our buffers to OS page mapping code here. + * + */ + memset(os_pages_status, 0xff, sizeof(int) * os_page_count); + + if (firstNumaTouch) + elog(DEBUG1, "NUMA: page-faulting the buffercache for proper NUMA readouts"); + + /* + * Scan through all the buffers, saving the relevant fields in the + * fctx->record structure. + * + * We don't hold the partition locks, so we don't get a consistent + * snapshot across all buffers, but we do grab the buffer header + * locks, so the information of each buffer is self-consistent. + */ + for (i = 0; i < NBuffers; i++) + { + pg_buffercache_save_tuple(i, fctx); + pg_buffercache_numa_prepare_ptrs(i, pages_per_blk, os_page_size, + os_page_ptrs); + } + + if (pg_numa_query_pages(0, os_page_count, os_page_ptrs, os_pages_status) == -1) + elog(ERROR, "failed NUMA pages inquiry: %m"); + + for (i = 0; i < NBuffers; i++) + { + int blk2page = (int) i * pages_per_blk; + + /* + * Set the NUMA node id for this buffer based on the first OS page + * it maps to. + * + * Note: We could check for errors in os_pages_status and report + * them. Also, a single DB block might span multiple NUMA nodes if + * it crosses OS pages on node boundaries, but we only record the + * node of the first page. This is a simplification but should be + * sufficient for most analyses. + */ + fctx->record[i].numa_node_id = os_pages_status[blk2page]; + } + } + + funcctx = SRF_PERCALL_SETUP(); + + /* Get the saved state */ + fctx = funcctx->user_fctx; + + if (funcctx->call_cntr < funcctx->max_calls) + { + Datum result; + uint32 i = funcctx->call_cntr; + + result = get_buffercache_tuple(i, fctx); + SRF_RETURN_NEXT(funcctx, result); + } + else + { + firstNumaTouch = false; + SRF_RETURN_DONE(funcctx); + } +} + Datum pg_buffercache_summary(PG_FUNCTION_ARGS) { diff --git a/contrib/pg_buffercache/sql/pg_buffercache_numa.sql b/contrib/pg_buffercache/sql/pg_buffercache_numa.sql new file mode 100644 index 00000000000..2225b879f58 --- /dev/null +++ b/contrib/pg_buffercache/sql/pg_buffercache_numa.sql @@ -0,0 +1,20 @@ +SELECT NOT(pg_numa_available()) AS skip_test \gset +\if :skip_test +\quit +\endif + +select count(*) = (select setting::bigint + from pg_settings + where name = 'shared_buffers') +from pg_buffercache_numa; + +-- Check that the functions / views can't be accessed by default. To avoid +-- having to create a dedicated user, use the pg_database_owner pseudo-role. +SET ROLE pg_database_owner; +SELECT count(*) > 0 FROM pg_buffercache_numa; +RESET role; + +-- Check that pg_monitor is allowed to query view / function +SET ROLE pg_monitor; +SELECT count(*) > 0 FROM pg_buffercache_numa; +RESET role; diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml index 802a5112d77..086e0062a17 100644 --- a/doc/src/sgml/pgbuffercache.sgml +++ b/doc/src/sgml/pgbuffercache.sgml @@ -30,7 +30,9 @@ This module provides the pg_buffercache_pages() function (wrapped in the pg_buffercache view), - the pg_buffercache_summary() function, the + pg_buffercache_numa_pages() function (wrapped in the + pg_buffercache_numa view), the + pg_buffercache_summary() function, the pg_buffercache_usage_counts() function and the pg_buffercache_evict() function. @@ -42,6 +44,14 @@ convenient use. + + The pg_buffercache_numa_pages() provides the same information + as pg_buffercache_pages() but is slower because it also + provides the NUMA node ID per shared buffer entry. + The pg_buffercache_numa view wraps the function for + convenient use. + + The pg_buffercache_summary() function returns a single row summarizing the state of the shared buffer cache. @@ -200,6 +210,55 @@ + + The <structname>pg_buffercache_numa</structname> View + + + The definitions of the columns exposed are identical to the + pg_buffercache view, except that this one includes + one additional node_id column as defined in + . + + + + <structname>pg_buffercache_numa</structname> Extra column + + + + + Column Type + + + Description + + + + + + + + node_id integer + + + NUMA node ID. NULL if the shared buffer + has not been used yet. On systems without NUMA support + this returns 0. + + + + + +
+ + + As NUMA node ID inquiry for each page requires memory pages + to be paged-in, the first execution of this function can take a noticeable + amount of time. In all the cases (first execution or not), retrieving this + information is costly and querying the view at a high frequency is not recommended. + + + + The <function>pg_buffercache_summary()</function> Function -- 2.49.0