From 88624ea0f768ebf1a015cc0c06d2c72c822577a8 Mon Sep 17 00:00:00 2001 From: Nazir Bilal Yavuz Date: Fri, 4 Apr 2025 13:22:00 +0300 Subject: [PATCH v6 1/4] Return buffer flushed information in pg_buffercache_evict function pg_buffercache_evict() function shows buffer flushed information now. This feature will be used in the following commits. Author: Nazir Bilal Yavuz Suggested-by: Joseph Koshakow Reviewed-by: Aidar Imamov Reviewed-by: Andres Freund Discussion: https://postgr.es/m/CAN55FZ0h_YoSqqutxV6DES1RW8ig6wcA8CR9rJk358YRMxZFmw%40mail.gmail.com --- src/include/storage/bufmgr.h | 2 +- src/backend/storage/buffer/bufmgr.c | 11 +++++++++- src/test/modules/test_aio/test_aio.c | 4 ++-- doc/src/sgml/pgbuffercache.sgml | 15 ++++++++----- contrib/pg_buffercache/Makefile | 3 ++- contrib/pg_buffercache/meson.build | 1 + .../pg_buffercache--1.5--1.6.sql | 9 ++++++++ contrib/pg_buffercache/pg_buffercache.control | 2 +- contrib/pg_buffercache/pg_buffercache_pages.c | 22 +++++++++++++++++-- 9 files changed, 55 insertions(+), 14 deletions(-) create mode 100644 contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..fab65824b18 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -304,7 +304,7 @@ extern uint32 GetAdditionalLocalPinLimit(void); extern void LimitAdditionalPins(uint32 *additional_pins); extern void LimitAdditionalLocalPins(uint32 *additional_pins); -extern bool EvictUnpinnedBuffer(Buffer buf); +extern bool EvictUnpinnedBuffer(Buffer buf, bool *flushed); /* in buf_init.c */ extern void BufferManagerShmemInit(void); diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 1c37d7dfe2f..e585b72e5fa 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -6508,17 +6508,24 @@ ResOwnerPrintBufferPin(Datum res) * even by the same block. This inherent raciness without other interlocking * makes the function unsuitable for non-testing usage. * + * *flushed is optional. If it is provided, it is set to true if the buffer + * was dirty and has been flushed. However, this does not necessarily mean + * that we flushed the buffer, it could have been flushed by someone else. + * * Returns true if the buffer was valid and it has now been made invalid. * Returns false if it wasn't valid, if it couldn't be evicted due to a pin, * or if the buffer becomes dirty again while we're trying to write it out. */ bool -EvictUnpinnedBuffer(Buffer buf) +EvictUnpinnedBuffer(Buffer buf, bool *flushed) { BufferDesc *desc; uint32 buf_state; bool result; + if (flushed) + *flushed = false; + /* Make sure we can pin the buffer. */ ResourceOwnerEnlarge(CurrentResourceOwner); ReservePrivateRefCountEntry(); @@ -6548,6 +6555,8 @@ EvictUnpinnedBuffer(Buffer buf) { LWLockAcquire(BufferDescriptorGetContentLock(desc), LW_SHARED); FlushBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL); + if (flushed) + *flushed = true; LWLockRelease(BufferDescriptorGetContentLock(desc)); } diff --git a/src/test/modules/test_aio/test_aio.c b/src/test/modules/test_aio/test_aio.c index bef0ecd9007..f9cf6ce8a26 100644 --- a/src/test/modules/test_aio/test_aio.c +++ b/src/test/modules/test_aio/test_aio.c @@ -237,7 +237,7 @@ modify_rel_block(PG_FUNCTION_ARGS) if (BufferIsLocal(buf)) InvalidateLocalBuffer(GetLocalBufferDescriptor(-buf - 1), true); else - EvictUnpinnedBuffer(buf); + EvictUnpinnedBuffer(buf, NULL); /* * Now modify the page as asked for by the caller. @@ -493,7 +493,7 @@ invalidate_rel_block(PG_FUNCTION_ARGS) if (BufferIsLocal(buf)) InvalidateLocalBuffer(GetLocalBufferDescriptor(-buf - 1), true); - else if (!EvictUnpinnedBuffer(buf)) + else if (!EvictUnpinnedBuffer(buf, NULL)) elog(ERROR, "couldn't evict"); } } diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml index 802a5112d77..187e13e8cda 100644 --- a/doc/src/sgml/pgbuffercache.sgml +++ b/doc/src/sgml/pgbuffercache.sgml @@ -369,12 +369,15 @@ The pg_buffercache_evict() function takes a buffer identifier, as shown in the bufferid column of - the pg_buffercache view. It returns true on success, - and false if the buffer wasn't valid, if it couldn't be evicted because it - was pinned, or if it became dirty again after an attempt to write it out. - The result is immediately out of date upon return, as the buffer might - become valid again at any time due to concurrent activity. The function is - intended for developer testing only. + the pg_buffercache view. It returns the + information about whether the buffer is evicted and flushed. evicted + column is true on success, and false if the buffer wasn't valid, if it + couldn't be evicted because it was pinned, or if it became dirty again + after an attempt to write it out. flushed column is true if the buffer is + flushed. This does not necessarily mean that buffer is flushed by us, it + might be flushed by someone else. The result is immediately out of date + upon return, as the buffer might become valid again at any time due to + concurrent activity. The function is intended for developer testing only. 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/meson.build b/contrib/pg_buffercache/meson.build index 12d1fe48717..9b2e9393410 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, ) 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..18597923af8 --- /dev/null +++ b/contrib/pg_buffercache/pg_buffercache--1.5--1.6.sql @@ -0,0 +1,9 @@ +\echo Use "ALTER EXTENSION pg_buffercache UPDATE TO '1.6'" to load this file. \quit + +DROP FUNCTION pg_buffercache_evict(integer); +CREATE FUNCTION pg_buffercache_evict( + IN int, + OUT evicted boolean, + OUT flushed boolean) +AS 'MODULE_PATHNAME', 'pg_buffercache_evict' +LANGUAGE C PARALLEL SAFE VOLATILE STRICT; 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 62602af1775..9493a40e804 100644 --- a/contrib/pg_buffercache/pg_buffercache_pages.c +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -19,6 +19,7 @@ #define NUM_BUFFERCACHE_PAGES_ELEM 9 #define NUM_BUFFERCACHE_SUMMARY_ELEM 5 #define NUM_BUFFERCACHE_USAGE_COUNTS_ELEM 4 +#define NUM_BUFFERCACHE_EVICT_ELEM 2 PG_MODULE_MAGIC_EXT( .name = "pg_buffercache", @@ -358,15 +359,32 @@ pg_buffercache_usage_counts(PG_FUNCTION_ARGS) Datum pg_buffercache_evict(PG_FUNCTION_ARGS) { + Datum result; + TupleDesc tupledesc; + HeapTuple tuple; + Datum values[NUM_BUFFERCACHE_EVICT_ELEM]; + bool nulls[NUM_BUFFERCACHE_EVICT_ELEM] = {0}; + Buffer buf = PG_GETARG_INT32(0); + bool flushed; + + if (get_call_result_type(fcinfo, NULL, &tupledesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); if (!superuser()) ereport(ERROR, (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), - errmsg("must be superuser to use pg_buffercache_evict function"))); + errmsg("must be superuser to use %s()", + "pg_buffercache_evict"))); if (buf < 1 || buf > NBuffers) elog(ERROR, "bad buffer ID: %d", buf); - PG_RETURN_BOOL(EvictUnpinnedBuffer(buf)); + values[0] = BoolGetDatum(EvictUnpinnedBuffer(buf, &flushed)); + values[1] = BoolGetDatum(flushed); + + tuple = heap_form_tuple(tupledesc, values, nulls); + result = HeapTupleGetDatum(tuple); + + PG_RETURN_DATUM(result); } -- 2.47.2