From e3ede35374549810c52581e0c98c9ec4437af59e Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Thu, 24 Nov 2022 18:20:36 -0800 Subject: [PATCH v13 1/3] Add eager and lazy freezing strategies to VACUUM. Avoid large build-ups of all-visible pages by making non-aggressive VACUUMs freeze pages proactively for VACUUMs/tables where eager vacuuming is deemed appropriate. VACUUM determines its freezing strategy based on the value of the new vacuum_freeze_strategy_threshold GUC (or reloption) in most cases: Tables that exceeds the size threshold use the eager freezing strategy. Otherwise VACUUM uses the lazy freezing strategy, which is essentially the same approach that VACUUM has always taken to freezing (though not quite, due to the influence of page level freezing following recent work). When the eager strategy is in use, lazy_scan_prune will trigger freezing a page's tuples at the point that it notices that it will at least become all-visible -- it can be made all-frozen instead. We still respect FreezeLimit, though: the presence of any XID < FreezeLimit also triggers page-level freezing (just as it would with the lazy strategy). Eager freezing is generally only applied when vacuuming larger tables, where freezing most individual heap pages at the first opportunity (in the first VACUUM operation where they can definitely be set all-visible) will improve performance stability. A later commit will add vmsnap scanning strategies, which are designed to work in tandem with the freezing strategies from this commit. Author: Peter Geoghegan Reviewed-By: Jeff Davis Reviewed-By: Andres Freund Discussion: https://postgr.es/m/CAH2-WzkFok_6EAHuK39GaW4FjEFQsY=3J0AAd6FXk93u-Xq3Fg@mail.gmail.com --- src/include/commands/vacuum.h | 10 +++++ src/include/utils/rel.h | 1 + src/backend/access/common/reloptions.c | 11 +++++ src/backend/access/heap/heapam.c | 1 + src/backend/access/heap/vacuumlazy.c | 43 ++++++++++++++++++- src/backend/commands/vacuum.c | 17 +++++++- src/backend/postmaster/autovacuum.c | 10 +++++ src/backend/utils/misc/guc_tables.c | 11 +++++ src/backend/utils/misc/postgresql.conf.sample | 1 + doc/src/sgml/config.sgml | 19 +++++++- doc/src/sgml/ref/create_table.sgml | 14 ++++++ doc/src/sgml/ref/vacuum.sgml | 16 +++---- 12 files changed, 143 insertions(+), 11 deletions(-) diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h index 2f274f2be..b39178d5b 100644 --- a/src/include/commands/vacuum.h +++ b/src/include/commands/vacuum.h @@ -220,6 +220,9 @@ typedef struct VacuumParams * use default */ int multixact_freeze_table_age; /* multixact age at which to scan * whole table */ + int freeze_strategy_threshold; /* threshold to use eager + * freezing, in total heap blocks, + * -1 to use default */ bool is_wraparound; /* force a for-wraparound vacuum */ int log_min_duration; /* minimum execution threshold in ms at * which autovacuum is logged, -1 to use @@ -272,6 +275,12 @@ struct VacuumCutoffs */ TransactionId FreezeLimit; MultiXactId MultiXactCutoff; + + /* + * Threshold cutoff point (expressed in # of physical heap rel blocks in + * rel's main fork) that triggers VACUUM's eager freezing strategy + */ + BlockNumber freeze_strategy_threshold; }; /* @@ -295,6 +304,7 @@ extern PGDLLIMPORT int vacuum_freeze_min_age; extern PGDLLIMPORT int vacuum_freeze_table_age; extern PGDLLIMPORT int vacuum_multixact_freeze_min_age; extern PGDLLIMPORT int vacuum_multixact_freeze_table_age; +extern PGDLLIMPORT int vacuum_freeze_strategy_threshold; extern PGDLLIMPORT int vacuum_failsafe_age; extern PGDLLIMPORT int vacuum_multixact_failsafe_age; diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h index f383a2fca..e195b63d7 100644 --- a/src/include/utils/rel.h +++ b/src/include/utils/rel.h @@ -308,6 +308,7 @@ typedef struct AutoVacOpts int vacuum_ins_threshold; int analyze_threshold; int vacuum_cost_limit; + int freeze_strategy_threshold; int freeze_min_age; int freeze_max_age; int freeze_table_age; diff --git a/src/backend/access/common/reloptions.c b/src/backend/access/common/reloptions.c index 75b734489..4b680501c 100644 --- a/src/backend/access/common/reloptions.c +++ b/src/backend/access/common/reloptions.c @@ -260,6 +260,15 @@ static relopt_int intRelOpts[] = }, -1, 1, 10000 }, + { + { + "autovacuum_freeze_strategy_threshold", + "Table size at which VACUUM freezes using eager strategy.", + RELOPT_KIND_HEAP | RELOPT_KIND_TOAST, + ShareUpdateExclusiveLock + }, + -1, 0, INT_MAX + }, { { "autovacuum_freeze_min_age", @@ -1851,6 +1860,8 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind) offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, analyze_threshold)}, {"autovacuum_vacuum_cost_limit", RELOPT_TYPE_INT, offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, vacuum_cost_limit)}, + {"autovacuum_freeze_strategy_threshold", RELOPT_TYPE_INT, + offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, freeze_strategy_threshold)}, {"autovacuum_freeze_min_age", RELOPT_TYPE_INT, offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, freeze_min_age)}, {"autovacuum_freeze_max_age", RELOPT_TYPE_INT, diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index 34d83dc70..3a8f50c31 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -6879,6 +6879,7 @@ heap_freeze_tuple(HeapTupleHeader tuple, cutoffs.OldestMxact = MultiXactCutoff; cutoffs.FreezeLimit = FreezeLimit; cutoffs.MultiXactCutoff = MultiXactCutoff; + cutoffs.freeze_strategy_threshold = 0; pagefrz.freeze_required = true; pagefrz.FreezePageRelfrozenXid = FreezeLimit; diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c index 9923994b5..0444b3f12 100644 --- a/src/backend/access/heap/vacuumlazy.c +++ b/src/backend/access/heap/vacuumlazy.c @@ -153,6 +153,8 @@ typedef struct LVRelState bool aggressive; /* Use visibility map to skip? (disabled by DISABLE_PAGE_SKIPPING) */ bool skipwithvm; + /* Eagerly freeze all tuples on pages about to be set all-visible? */ + bool eager_freeze_strategy; /* Wraparound failsafe has been triggered? */ bool failsafe_active; /* Consider index vacuuming bypass optimization? */ @@ -242,6 +244,7 @@ typedef struct LVSavedErrInfo /* non-export function prototypes */ static void lazy_scan_heap(LVRelState *vacrel); +static void lazy_scan_strategy(LVRelState *vacrel); static BlockNumber lazy_scan_skip(LVRelState *vacrel, Buffer *vmbuffer, BlockNumber next_block, bool *next_unskippable_allvis, @@ -470,6 +473,10 @@ heap_vacuum_rel(Relation rel, VacuumParams *params, vacrel->skipwithvm = skipwithvm; + /* + * Now determine VACUUM's freezing strategy. + */ + lazy_scan_strategy(vacrel); if (verbose) { if (vacrel->aggressive) @@ -1249,6 +1256,38 @@ lazy_scan_heap(LVRelState *vacrel) lazy_cleanup_all_indexes(vacrel); } +/* + * lazy_scan_strategy() -- Determine freezing strategy. + * + * Our lazy freezing strategy is useful when putting off the work of freezing + * totally avoids freezing that turns out to have been wasted effort later on. + * Our eager freezing strategy is useful with larger tables that experience + * continual growth, where freezing pages proactively is needed just to avoid + * falling behind on freezing (eagerness is also likely to be cheaper in the + * short/medium term for such tables, but the long term picture matters most). + */ +static void +lazy_scan_strategy(LVRelState *vacrel) +{ + BlockNumber rel_pages = vacrel->rel_pages; + + /* + * Decide freezing strategy. + * + * The eager freezing strategy is used when the threshold controlled by + * freeze_strategy_threshold GUC/reloption exceeds rel_pages. + * + * Also freeze eagerly with an unlogged or temp table, where the total + * cost of freezing each page is just the cycles needed to prepare a set + * of freeze plans. Executing the freeze plans adds very little cost. + * Dirtying extra pages isn't a concern, either; VACUUM will definitely + * set PD_ALL_VISIBLE on affected pages, regardless of freezing strategy. + */ + vacrel->eager_freeze_strategy = + (rel_pages >= vacrel->cutoffs.freeze_strategy_threshold || + !RelationIsPermanent(vacrel->rel)); +} + /* * lazy_scan_skip() -- set up range of skippable blocks using visibility map. * @@ -1771,10 +1810,12 @@ retry: * one XID/MXID from before FreezeLimit/MultiXactCutoff is present. Also * freeze when pruning generated an FPI, if doing so means that we set the * page all-frozen afterwards (might not happen until final heap pass). + * When ongoing VACUUM opted to use the eager freezing strategy, we freeze + * any page that will thereby become all-frozen in the visibility map. */ if (pagefrz.freeze_required || tuples_frozen == 0 || (prunestate->all_visible && prunestate->all_frozen && - fpi_before != pgWalUsage.wal_fpi)) + (fpi_before != pgWalUsage.wal_fpi || vacrel->eager_freeze_strategy))) { /* * We're freezing the page. Our final NewRelfrozenXid doesn't need to diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index ba965b8c7..7c68bd8ff 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -67,6 +67,7 @@ int vacuum_freeze_min_age; int vacuum_freeze_table_age; int vacuum_multixact_freeze_min_age; int vacuum_multixact_freeze_table_age; +int vacuum_freeze_strategy_threshold; int vacuum_failsafe_age; int vacuum_multixact_failsafe_age; @@ -263,6 +264,9 @@ ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel) params.multixact_freeze_table_age = -1; } + /* Determine freezing strategy later on using GUC or reloption */ + params.freeze_strategy_threshold = -1; + /* user-invoked vacuum is never "for wraparound" */ params.is_wraparound = false; @@ -926,7 +930,8 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams *params, multixact_freeze_min_age, freeze_table_age, multixact_freeze_table_age, - effective_multixact_freeze_max_age; + effective_multixact_freeze_max_age, + freeze_strategy_threshold; TransactionId nextXID, safeOldestXmin, aggressiveXIDCutoff; @@ -939,6 +944,7 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams *params, multixact_freeze_min_age = params->multixact_freeze_min_age; freeze_table_age = params->freeze_table_age; multixact_freeze_table_age = params->multixact_freeze_table_age; + freeze_strategy_threshold = params->freeze_strategy_threshold; /* Set pg_class fields in cutoffs */ cutoffs->relfrozenxid = rel->rd_rel->relfrozenxid; @@ -1053,6 +1059,15 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams *params, if (MultiXactIdPrecedes(cutoffs->OldestMxact, cutoffs->MultiXactCutoff)) cutoffs->MultiXactCutoff = cutoffs->OldestMxact; + /* + * Determine the freeze_strategy_threshold to use: as specified by the + * caller, or vacuum_freeze_strategy_threshold + */ + if (freeze_strategy_threshold < 0) + freeze_strategy_threshold = vacuum_freeze_strategy_threshold; + Assert(freeze_strategy_threshold >= 0); + cutoffs->freeze_strategy_threshold = freeze_strategy_threshold; + /* * Finally, figure out if caller needs to do an aggressive VACUUM or not. * diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index 0746d8022..23e316e59 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -151,6 +151,7 @@ static int default_freeze_min_age; static int default_freeze_table_age; static int default_multixact_freeze_min_age; static int default_multixact_freeze_table_age; +static int default_freeze_strategy_threshold; /* Memory context for long-lived data */ static MemoryContext AutovacMemCxt; @@ -2010,6 +2011,7 @@ do_autovacuum(void) default_freeze_table_age = 0; default_multixact_freeze_min_age = 0; default_multixact_freeze_table_age = 0; + default_freeze_strategy_threshold = 0; } else { @@ -2017,6 +2019,7 @@ do_autovacuum(void) default_freeze_table_age = vacuum_freeze_table_age; default_multixact_freeze_min_age = vacuum_multixact_freeze_min_age; default_multixact_freeze_table_age = vacuum_multixact_freeze_table_age; + default_freeze_strategy_threshold = vacuum_freeze_strategy_threshold; } ReleaseSysCache(tuple); @@ -2801,6 +2804,7 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map, int freeze_table_age; int multixact_freeze_min_age; int multixact_freeze_table_age; + int freeze_strategy_threshold; int vac_cost_limit; double vac_cost_delay; int log_min_duration; @@ -2850,6 +2854,11 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map, ? avopts->multixact_freeze_table_age : default_multixact_freeze_table_age; + freeze_strategy_threshold = (avopts && + avopts->freeze_strategy_threshold >= 0) + ? avopts->freeze_strategy_threshold + : default_freeze_strategy_threshold; + tab = palloc(sizeof(autovac_table)); tab->at_relid = relid; tab->at_sharedrel = classForm->relisshared; @@ -2872,6 +2881,7 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map, tab->at_params.freeze_table_age = freeze_table_age; tab->at_params.multixact_freeze_min_age = multixact_freeze_min_age; tab->at_params.multixact_freeze_table_age = multixact_freeze_table_age; + tab->at_params.freeze_strategy_threshold = freeze_strategy_threshold; tab->at_params.is_wraparound = wraparound; tab->at_params.log_min_duration = log_min_duration; tab->at_vacuum_cost_limit = vac_cost_limit; diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index a37c9f984..f6aae528d 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -2524,6 +2524,17 @@ struct config_int ConfigureNamesInt[] = NULL, NULL, NULL }, + { + {"vacuum_freeze_strategy_threshold", PGC_USERSET, CLIENT_CONN_STATEMENT, + gettext_noop("Table size at which VACUUM freezes using eager strategy."), + NULL, + GUC_UNIT_BLOCKS + }, + &vacuum_freeze_strategy_threshold, + (UINT64CONST(4) * 1024 * 1024 * 1024) / BLCKSZ, 0, INT_MAX, + NULL, NULL, NULL + }, + { {"vacuum_defer_cleanup_age", PGC_SIGHUP, REPLICATION_PRIMARY, gettext_noop("Number of transactions by which VACUUM and HOT cleanup should be deferred, if any."), diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 5afdeb04d..447645b73 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -693,6 +693,7 @@ #idle_in_transaction_session_timeout = 0 # in milliseconds, 0 is disabled #idle_session_timeout = 0 # in milliseconds, 0 is disabled #vacuum_freeze_table_age = 150000000 +#vacuum_freeze_strategy_threshold = 4GB #vacuum_freeze_min_age = 50000000 #vacuum_failsafe_age = 1600000000 #vacuum_multixact_freeze_table_age = 150000000 diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 05b3862d0..b1137381a 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -9161,6 +9161,21 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; + + vacuum_freeze_strategy_threshold (integer) + + vacuum_freeze_strategy_threshold configuration parameter + + + + + Specifies the cutoff size (in pages) that VACUUM + should use to decide whether to apply its eager freezing strategy. + The default is 4 gigabytes (4GB). + + + + vacuum_freeze_table_age (integer) @@ -9196,7 +9211,9 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; Specifies the cutoff age (in transactions) that VACUUM should use to decide whether to - trigger freezing of pages that have an older XID. + trigger freezing of pages that have an older XID. When VACUUM + uses its eager freezing strategy, freezing a page can also be + triggered when the page contains only all-visible tuples. The default is 50 million transactions. Although users can set this value anywhere from zero to one billion, VACUUM will silently limit the effective value to half diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml index c98223b2a..eabbf9e65 100644 --- a/doc/src/sgml/ref/create_table.sgml +++ b/doc/src/sgml/ref/create_table.sgml @@ -1682,6 +1682,20 @@ WITH ( MODULUS numeric_literal, REM + + autovacuum_freeze_strategy_threshold, toast.autovacuum_freeze_strategy_threshold (integer) + + autovacuum_freeze_strategy_threshold storage parameter + + + + + Per-table value for + parameter. + + + + autovacuum_freeze_min_age, toast.autovacuum_freeze_min_age (integer) diff --git a/doc/src/sgml/ref/vacuum.sgml b/doc/src/sgml/ref/vacuum.sgml index e14ead882..79595b1cb 100644 --- a/doc/src/sgml/ref/vacuum.sgml +++ b/doc/src/sgml/ref/vacuum.sgml @@ -119,14 +119,14 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ and - parameters - set to zero. Aggressive freezing is always performed when the - table is rewritten, so this option is redundant when FULL - is specified. + Selects eager freezing of tuples. Specifying + FREEZE is equivalent to performing + VACUUM with the and parameters set + to zero. Eager freezing is always performed when the table is + rewritten, so this option is redundant when + FULL is specified. -- 2.38.1