From c1b911cffbbb52a4479f1b47318c4d73bb671bb6 Mon Sep 17 00:00:00 2001 From: Maxim Orlov Date: Wed, 7 Aug 2024 16:35:22 +0300 Subject: [PATCH v19 1/5] Use 64-bit multixact offsets Switching to 64-bit multitransaction offsets removes wraparound and the 2^32 limit on their total number. On the other hand, this move is inevitable in increased disc space utilisation. Fortunately, multitransaction offsets rise monotonically and without gaps. To conserve disc space consumed by segments, we write a 64-bit "base" at the start of each page, which also serves as the page's first offset. All subsequent offsets on the page are calculated relative to this "base". Author: Maxim Orlov --- src/backend/access/rmgrdesc/mxactdesc.c | 4 +- src/backend/access/rmgrdesc/xlogdesc.c | 2 +- src/backend/access/transam/multixact.c | 375 +++++++--------------- src/backend/access/transam/xlogrecovery.c | 2 +- src/backend/commands/vacuum.c | 2 +- src/backend/postmaster/autovacuum.c | 4 +- src/bin/pg_controldata/pg_controldata.c | 2 +- src/bin/pg_resetwal/pg_resetwal.c | 6 +- src/bin/pg_resetwal/t/001_basic.pl | 2 +- src/include/access/multixact.h | 3 +- src/include/c.h | 2 +- 11 files changed, 125 insertions(+), 279 deletions(-) diff --git a/src/backend/access/rmgrdesc/mxactdesc.c b/src/backend/access/rmgrdesc/mxactdesc.c index 3ca0582db3..052dd0a4ce 100644 --- a/src/backend/access/rmgrdesc/mxactdesc.c +++ b/src/backend/access/rmgrdesc/mxactdesc.c @@ -65,7 +65,7 @@ multixact_desc(StringInfo buf, XLogReaderState *record) xl_multixact_create *xlrec = (xl_multixact_create *) rec; int i; - appendStringInfo(buf, "%u offset %u nmembers %d: ", xlrec->mid, + appendStringInfo(buf, "%u offset %" PRIu64 " nmembers %d: ", xlrec->mid, xlrec->moff, xlrec->nmembers); for (i = 0; i < xlrec->nmembers; i++) out_member(buf, &xlrec->members[i]); @@ -74,7 +74,7 @@ multixact_desc(StringInfo buf, XLogReaderState *record) { xl_multixact_truncate *xlrec = (xl_multixact_truncate *) rec; - appendStringInfo(buf, "offsets [%u, %u), members [%u, %u)", + appendStringInfo(buf, "offsets [%u, %u), members [%" PRIu64 ", %" PRIu64 ")", xlrec->startTruncOff, xlrec->endTruncOff, xlrec->startTruncMemb, xlrec->endTruncMemb); } diff --git a/src/backend/access/rmgrdesc/xlogdesc.c b/src/backend/access/rmgrdesc/xlogdesc.c index cd6c2a2f65..441034f592 100644 --- a/src/backend/access/rmgrdesc/xlogdesc.c +++ b/src/backend/access/rmgrdesc/xlogdesc.c @@ -66,7 +66,7 @@ xlog_desc(StringInfo buf, XLogReaderState *record) CheckPoint *checkpoint = (CheckPoint *) rec; appendStringInfo(buf, "redo %X/%08X; " - "tli %u; prev tli %u; fpw %s; wal_level %s; xid %u:%u; oid %u; multi %u; offset %u; " + "tli %u; prev tli %u; fpw %s; wal_level %s; xid %u:%u; oid %u; multi %u; offset %" PRIu64 "; " "oldest xid %u in DB %u; oldest multi %u in DB %u; " "oldest/newest commit timestamp xid: %u/%u; " "oldest running xid %u; %s", diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 9d5f130af7..e7861614be 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -89,21 +89,31 @@ #include "utils/memutils.h" +typedef int32 ShortMultiXactOffset; /* for a disk storage */ + /* * Defines for MultiXactOffset page sizes. A page is the same BLCKSZ as is * used everywhere else in Postgres. * - * Note: because MultiXactOffsets are 32 bits and wrap around at 0xFFFFFFFF, - * MultiXact page numbering also wraps around at - * 0xFFFFFFFF/MULTIXACT_OFFSETS_PER_PAGE, and segment numbering at - * 0xFFFFFFFF/MULTIXACT_OFFSETS_PER_PAGE/SLRU_PAGES_PER_SEGMENT. We need - * take no explicit notice of that fact in this module, except when comparing - * segment and page numbers in TruncateMultiXact (see - * MultiXactOffsetPagePrecedes). + * There are two key factors why utilising straightforward 64-bit offset values + * for is wasteful in terms of disc space usage: + * 1) offset values are recorded in ascending order and not overwritten; + * 2) the largest supported BLCKSZ is 32k, which can store up to 2^13 32-bit + * items on a single page; thus, with MAX_BACKENDS limited to 2^18-1 we have + * 2^13 * (2^18-1) which is less 2^31 and fits 32-bits. + * + * In other words, max "distance" for offsets on a single page is not exeeded + * 32-bits. To optimise disc space allocation, we employ the following scheme. + * On each page, the basic 64-bit offset, known as the page base, is located + * first. Next, there are 32-bit deltas relative to the base element are + * placed. Thus, the required offset for the 0-th element is the page's + * base; the value for each subsequent offset on the same page is calculated + * by adding it to the page base (0-th) element. */ -/* We need four bytes per offset */ -#define MULTIXACT_OFFSETS_PER_PAGE (BLCKSZ / sizeof(MultiXactOffset)) +/* We need four bytes per offset, 8 bytes for the base */ +#define MULTIXACT_OFFSETS_PER_PAGE \ + ((BLCKSZ - sizeof(MultiXactOffset)) / sizeof(ShortMultiXactOffset)) static inline int64 MultiXactIdToOffsetPage(MultiXactId multi) @@ -208,10 +218,14 @@ MXOffsetToMemberOffset(MultiXactOffset offset) member_in_group * sizeof(TransactionId); } -/* Multixact members wraparound thresholds. */ -#define MULTIXACT_MEMBER_SAFE_THRESHOLD (MaxMultiXactOffset / 2) -#define MULTIXACT_MEMBER_DANGER_THRESHOLD \ - (MaxMultiXactOffset - MaxMultiXactOffset / 4) +/* + * Multixact members warning threshold. + * + * If difference bettween nextOffset and oldestOffset exceed this value, we + * trigger autovacuumin order to release the disk space, reduce table bloat if + * possible. + */ +#define MULTIXACT_MEMBER_AUTOVAC_THRESHOLD UINT64CONST(0xFFFFFFFF) static inline MultiXactId PreviousMultiXactId(MultiXactId multi) @@ -228,6 +242,51 @@ static SlruCtlData MultiXactMemberCtlData; #define MultiXactOffsetCtl (&MultiXactOffsetCtlData) #define MultiXactMemberCtl (&MultiXactMemberCtlData) +/* + * To avoid diving deep into address arithmetic, we declare an auxiliary + * structure that access the MultiXactOffset SLRU page. + */ +typedef struct MultiXactOffsetSLRUPage +{ + MultiXactOffset base; + ShortMultiXactOffset offset[FLEXIBLE_ARRAY_MEMBER]; +} MultiXactOffsetSLRUPage; + +static inline MultiXactOffset +MXOffsetRead(int entryno, int slotno) +{ + MultiXactOffsetSLRUPage *page = + (MultiXactOffsetSLRUPage *) MultiXactOffsetCtl->shared->page_buffer[slotno]; + + if (page->offset[entryno] != 0) + return page->base + (page->offset[entryno] ^ 0x80000000); + + return 0; +} + +static inline void +MXOffsetWrite(int entryno, int slotno, MultiXactOffset offset) +{ + MultiXactOffsetSLRUPage *page = + (MultiXactOffsetSLRUPage *) MultiXactOffsetCtl->shared->page_buffer[slotno]; + + if (page->base != 0) + page->offset[entryno] = offset - page->base; + else + { + page->base = offset; + page->offset[entryno] = 0; + } + + /* + * We need to distinguish between uninited value and not yet written offset. + * See case 2 in GetMultiXactIdMembers. + * + * So, mark this offset inited. + */ + page->offset[entryno] ^= 0x80000000; +} + /* * MultiXact state shared across all backends. All this state is protected * by MultiXactGenLock. (We also use SLRU bank's lock of MultiXactOffset and @@ -268,9 +327,6 @@ typedef struct MultiXactStateData MultiXactId multiStopLimit; MultiXactId multiWrapLimit; - /* support for members anti-wraparound measures */ - MultiXactOffset offsetStopLimit; /* known if oldestOffsetKnown */ - /* * This is used to sleep until a multixact offset is written when we want * to create the next one. @@ -401,8 +457,6 @@ static bool MultiXactOffsetPrecedes(MultiXactOffset offset1, MultiXactOffset offset2); static void ExtendMultiXactOffset(MultiXactId multi); static void ExtendMultiXactMember(MultiXactOffset offset, int nmembers); -static bool MultiXactOffsetWouldWrap(MultiXactOffset boundary, - MultiXactOffset start, uint32 distance); static bool SetOffsetVacuumLimit(bool is_startup); static bool find_multixact_start(MultiXactId multi, MultiXactOffset *result); static void WriteMTruncateXlogRec(Oid oldestMultiDB, @@ -911,7 +965,6 @@ RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, int64 prev_pageno; int entryno; int slotno; - MultiXactOffset *offptr; int i; LWLock *lock; LWLock *prevlock = NULL; @@ -930,10 +983,8 @@ RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, * take the trouble to generalize the slru.c error reporting code. */ slotno = SimpleLruReadPage(MultiXactOffsetCtl, pageno, true, multi); - offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[slotno]; - offptr += entryno; - *offptr = offset; + MXOffsetWrite(entryno, slotno, offset); MultiXactOffsetCtl->shared->page_dirty[slotno] = true; @@ -1155,78 +1206,6 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset) else *offset = nextOffset; - /*---------- - * Protect against overrun of the members space as well, with the - * following rules: - * - * If we're past offsetStopLimit, refuse to generate more multis. - * If we're close to offsetStopLimit, emit a warning. - * - * Arbitrarily, we start emitting warnings when we're 20 segments or less - * from offsetStopLimit. - * - * Note we haven't updated the shared state yet, so if we fail at this - * point, the multixact ID we grabbed can still be used by the next guy. - * - * Note that there is no point in forcing autovacuum runs here: the - * multixact freeze settings would have to be reduced for that to have any - * effect. - *---------- - */ -#define OFFSET_WARN_SEGMENTS 20 - if (MultiXactState->oldestOffsetKnown && - MultiXactOffsetWouldWrap(MultiXactState->offsetStopLimit, nextOffset, - nmembers)) - { - /* see comment in the corresponding offsets wraparound case */ - SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER); - - ereport(ERROR, - (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), - errmsg("multixact \"members\" limit exceeded"), - errdetail_plural("This command would create a multixact with %u members, but the remaining space is only enough for %u member.", - "This command would create a multixact with %u members, but the remaining space is only enough for %u members.", - MultiXactState->offsetStopLimit - nextOffset - 1, - nmembers, - MultiXactState->offsetStopLimit - nextOffset - 1), - errhint("Execute a database-wide VACUUM in database with OID %u with reduced \"vacuum_multixact_freeze_min_age\" and \"vacuum_multixact_freeze_table_age\" settings.", - MultiXactState->oldestMultiXactDB))); - } - - /* - * Check whether we should kick autovacuum into action, to prevent members - * wraparound. NB we use a much larger window to trigger autovacuum than - * just the warning limit. The warning is just a measure of last resort - - * this is in line with GetNewTransactionId's behaviour. - */ - if (!MultiXactState->oldestOffsetKnown || - (MultiXactState->nextOffset - MultiXactState->oldestOffset - > MULTIXACT_MEMBER_SAFE_THRESHOLD)) - { - /* - * To avoid swamping the postmaster with signals, we issue the autovac - * request only when crossing a segment boundary. With default - * compilation settings that's roughly after 50k members. This still - * gives plenty of chances before we get into real trouble. - */ - if ((MXOffsetToMemberPage(nextOffset) / SLRU_PAGES_PER_SEGMENT) != - (MXOffsetToMemberPage(nextOffset + nmembers) / SLRU_PAGES_PER_SEGMENT)) - SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER); - } - - if (MultiXactState->oldestOffsetKnown && - MultiXactOffsetWouldWrap(MultiXactState->offsetStopLimit, - nextOffset, - nmembers + MULTIXACT_MEMBERS_PER_PAGE * SLRU_PAGES_PER_SEGMENT * OFFSET_WARN_SEGMENTS)) - ereport(WARNING, - (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), - errmsg_plural("database with OID %u must be vacuumed before %d more multixact member is used", - "database with OID %u must be vacuumed before %d more multixact members are used", - MultiXactState->offsetStopLimit - nextOffset + nmembers, - MultiXactState->oldestMultiXactDB, - MultiXactState->offsetStopLimit - nextOffset + nmembers), - errhint("Execute a database-wide VACUUM in that database with reduced \"vacuum_multixact_freeze_min_age\" and \"vacuum_multixact_freeze_table_age\" settings."))); - ExtendMultiXactMember(nextOffset, nmembers); /* @@ -1255,7 +1234,8 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset) LWLockRelease(MultiXactGenLock); - debug_elog4(DEBUG2, "GetNew: returning %u offset %u", result, *offset); + debug_elog4(DEBUG2, "GetNew: returning %u offset %" PRIu64, result, + *offset); return result; } @@ -1294,7 +1274,6 @@ GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, int64 prev_pageno; int entryno; int slotno; - MultiXactOffset *offptr; MultiXactOffset offset; int length; int truelength; @@ -1418,9 +1397,8 @@ retry: LWLockAcquire(lock, LW_EXCLUSIVE); slotno = SimpleLruReadPage(MultiXactOffsetCtl, pageno, true, multi); - offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[slotno]; - offptr += entryno; - offset = *offptr; + + offset = MXOffsetRead(entryno, slotno); Assert(offset != 0); @@ -1467,9 +1445,7 @@ retry: slotno = SimpleLruReadPage(MultiXactOffsetCtl, pageno, true, tmpMXact); } - offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[slotno]; - offptr += entryno; - nextMXOffset = *offptr; + nextMXOffset = MXOffsetRead(entryno, slotno); if (nextMXOffset == 0) { @@ -1973,7 +1949,7 @@ MultiXactShmemInit(void) "pg_multixact/members", LWTRANCHE_MULTIXACTMEMBER_BUFFER, LWTRANCHE_MULTIXACTMEMBER_SLRU, SYNC_HANDLER_MULTIXACT_MEMBER, - false); + true); /* doesn't call SimpleLruTruncate() or meet criteria for unit tests */ /* Initialize our shared state struct */ @@ -2149,9 +2125,24 @@ TrimMultiXact(void) LWLockAcquire(lock, LW_EXCLUSIVE); slotno = SimpleLruReadPage(MultiXactOffsetCtl, pageno, true, nextMXact); offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[slotno]; - offptr += entryno; - MemSet(offptr, 0, BLCKSZ - (entryno * sizeof(MultiXactOffset))); + if (entryno == 0) + MemSet(offptr, 0, BLCKSZ); + else + { + ShortMultiXactOffset *off32ptr; + + off32ptr = (ShortMultiXactOffset *) (offptr + 1); + off32ptr += entryno; + + /* + * Knowing that offptr points to the beginning of the buffer, + * address arithmetic can be used to determine the amount of + * bytes remaining. + */ + MemSet(off32ptr, 0, + BLCKSZ - (((char *) off32ptr - (char *) offptr))); + } MultiXactOffsetCtl->shared->page_dirty[slotno] = true; LWLockRelease(lock); @@ -2223,7 +2214,7 @@ MultiXactGetCheckptMulti(bool is_shutdown, LWLockRelease(MultiXactGenLock); debug_elog6(DEBUG2, - "MultiXact: checkpoint is nextMulti %u, nextOffset %u, oldestMulti %u in DB %u", + "MultiXact: checkpoint is nextMulti %u, nextOffset %" PRIu64 ", oldestMulti %u in DB %u", *nextMulti, *nextMultiOffset, *oldestMulti, *oldestMultiDB); } @@ -2258,7 +2249,7 @@ void MultiXactSetNextMXact(MultiXactId nextMulti, MultiXactOffset nextMultiOffset) { - debug_elog4(DEBUG2, "MultiXact: setting next multi to %u offset %u", + debug_elog4(DEBUG2, "MultiXact: setting next multi to %u offset %" PRIu64, nextMulti, nextMultiOffset); LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE); MultiXactState->nextMXact = nextMulti; @@ -2449,7 +2440,7 @@ MultiXactAdvanceNextMXact(MultiXactId minMulti, } if (MultiXactOffsetPrecedes(MultiXactState->nextOffset, minMultiOffset)) { - debug_elog3(DEBUG2, "MultiXact: setting next offset to %u", + debug_elog3(DEBUG2, "MultiXact: setting next offset to %" PRIU64, minMultiOffset); MultiXactState->nextOffset = minMultiOffset; } @@ -2633,15 +2624,13 @@ GetOldestMultiXactId(void) } /* - * Determine how aggressively we need to vacuum in order to prevent member - * wraparound. + * Determine if we need to vacuum for member or not. * * To do so determine what's the oldest member offset and install the limit * info in MultiXactState, where it can be used to prevent overrun of old data * in the members SLRU area. * - * The return value is true if emergency autovacuum is required and false - * otherwise. + * The return value is true if autovacuum is required and false otherwise. */ static bool SetOffsetVacuumLimit(bool is_startup) @@ -2653,8 +2642,6 @@ SetOffsetVacuumLimit(bool is_startup) MultiXactOffset nextOffset; bool oldestOffsetKnown = false; bool prevOldestOffsetKnown; - MultiXactOffset offsetStopLimit = 0; - MultiXactOffset prevOffsetStopLimit; /* * NB: Have to prevent concurrent truncation, we might otherwise try to @@ -2669,7 +2656,6 @@ SetOffsetVacuumLimit(bool is_startup) nextOffset = MultiXactState->nextOffset; prevOldestOffsetKnown = MultiXactState->oldestOffsetKnown; prevOldestOffset = MultiXactState->oldestOffset; - prevOffsetStopLimit = MultiXactState->offsetStopLimit; Assert(MultiXactState->finishedStartup); LWLockRelease(MultiXactGenLock); @@ -2700,11 +2686,7 @@ SetOffsetVacuumLimit(bool is_startup) oldestOffsetKnown = find_multixact_start(oldestMultiXactId, &oldestOffset); - if (oldestOffsetKnown) - ereport(DEBUG1, - (errmsg_internal("oldest MultiXactId member is at offset %u", - oldestOffset))); - else + if (!oldestOffsetKnown) ereport(LOG, (errmsg("MultiXact member wraparound protections are disabled because oldest checkpointed MultiXact %u does not exist on disk", oldestMultiXactId))); @@ -2717,24 +2699,7 @@ SetOffsetVacuumLimit(bool is_startup) * overrun of old data in the members SLRU area. We can only do so if the * oldest offset is known though. */ - if (oldestOffsetKnown) - { - /* move back to start of the corresponding segment */ - offsetStopLimit = oldestOffset - (oldestOffset % - (MULTIXACT_MEMBERS_PER_PAGE * SLRU_PAGES_PER_SEGMENT)); - - /* always leave one segment before the wraparound point */ - offsetStopLimit -= (MULTIXACT_MEMBERS_PER_PAGE * SLRU_PAGES_PER_SEGMENT); - - if (!prevOldestOffsetKnown && !is_startup) - ereport(LOG, - (errmsg("MultiXact member wraparound protections are now enabled"))); - - ereport(DEBUG1, - (errmsg_internal("MultiXact member stop limit is now %u based on MultiXact %u", - offsetStopLimit, oldestMultiXactId))); - } - else if (prevOldestOffsetKnown) + if (prevOldestOffsetKnown) { /* * If we failed to get the oldest offset this time, but we have a @@ -2744,69 +2709,19 @@ SetOffsetVacuumLimit(bool is_startup) */ oldestOffset = prevOldestOffset; oldestOffsetKnown = true; - offsetStopLimit = prevOffsetStopLimit; } /* Install the computed values */ LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE); MultiXactState->oldestOffset = oldestOffset; MultiXactState->oldestOffsetKnown = oldestOffsetKnown; - MultiXactState->offsetStopLimit = offsetStopLimit; LWLockRelease(MultiXactGenLock); /* - * Do we need an emergency autovacuum? If we're not sure, assume yes. + * Do we need autovacuum? If we're not sure, assume yes. */ return !oldestOffsetKnown || - (nextOffset - oldestOffset > MULTIXACT_MEMBER_SAFE_THRESHOLD); -} - -/* - * Return whether adding "distance" to "start" would move past "boundary". - * - * We use this to determine whether the addition is "wrapping around" the - * boundary point, hence the name. The reason we don't want to use the regular - * 2^31-modulo arithmetic here is that we want to be able to use the whole of - * the 2^32-1 space here, allowing for more multixacts than would fit - * otherwise. - */ -static bool -MultiXactOffsetWouldWrap(MultiXactOffset boundary, MultiXactOffset start, - uint32 distance) -{ - MultiXactOffset finish; - - /* - * Note that offset number 0 is not used (see GetMultiXactIdMembers), so - * if the addition wraps around the UINT_MAX boundary, skip that value. - */ - finish = start + distance; - if (finish < start) - finish++; - - /*----------------------------------------------------------------------- - * When the boundary is numerically greater than the starting point, any - * value numerically between the two is not wrapped: - * - * <----S----B----> - * [---) = F wrapped past B (and UINT_MAX) - * [---) = F not wrapped - * [----] = F wrapped past B - * - * When the boundary is numerically less than the starting point (i.e. the - * UINT_MAX wraparound occurs somewhere in between) then all values in - * between are wrapped: - * - * <----B----S----> - * [---) = F not wrapped past B (but wrapped past UINT_MAX) - * [---) = F wrapped past B (and UINT_MAX) - * [----] = F not wrapped - *----------------------------------------------------------------------- - */ - if (start < boundary) - return finish >= boundary || finish < start; - else - return finish >= boundary && finish < start; + (nextOffset - oldestOffset > MULTIXACT_MEMBER_AUTOVAC_THRESHOLD); } /* @@ -2825,7 +2740,6 @@ find_multixact_start(MultiXactId multi, MultiXactOffset *result) int64 pageno; int entryno; int slotno; - MultiXactOffset *offptr; Assert(MultiXactState->finishedStartup); @@ -2843,9 +2757,9 @@ find_multixact_start(MultiXactId multi, MultiXactOffset *result) /* lock is acquired by SimpleLruReadPage_ReadOnly */ slotno = SimpleLruReadPage_ReadOnly(MultiXactOffsetCtl, pageno, multi); - offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[slotno]; - offptr += entryno; - offset = *offptr; + + offset = MXOffsetRead(entryno, slotno); + LWLockRelease(SimpleLruGetBankLock(MultiXactOffsetCtl, pageno)); *result = offset; @@ -2893,73 +2807,6 @@ GetMultiXactInfo(uint32 *multixacts, MultiXactOffset *members, return true; } -/* - * Multixact members can be removed once the multixacts that refer to them - * are older than every datminmxid. autovacuum_multixact_freeze_max_age and - * vacuum_multixact_freeze_table_age work together to make sure we never have - * too many multixacts; we hope that, at least under normal circumstances, - * this will also be sufficient to keep us from using too many offsets. - * However, if the average multixact has many members, we might exhaust the - * members space while still using few enough members that these limits fail - * to trigger relminmxid advancement by VACUUM. At that point, we'd have no - * choice but to start failing multixact-creating operations with an error. - * - * To prevent that, if more than a threshold portion of the members space is - * used, we effectively reduce autovacuum_multixact_freeze_max_age and - * to a value just less than the number of multixacts in use. We hope that - * this will quickly trigger autovacuuming on the table or tables with the - * oldest relminmxid, thus allowing datminmxid values to advance and removing - * some members. - * - * As the fraction of the member space currently in use grows, we become - * more aggressive in clamping this value. That not only causes autovacuum - * to ramp up, but also makes any manual vacuums the user issues more - * aggressive. This happens because vacuum_get_cutoffs() will clamp the - * freeze table and the minimum freeze age cutoffs based on the effective - * autovacuum_multixact_freeze_max_age this function returns. In the worst - * case, we'll claim the freeze_max_age to zero, and every vacuum of any - * table will freeze every multixact. - */ -int -MultiXactMemberFreezeThreshold(void) -{ - MultiXactOffset members; - uint32 multixacts; - uint32 victim_multixacts; - double fraction; - int result; - MultiXactId oldestMultiXactId; - MultiXactOffset oldestOffset; - - /* If we can't determine member space utilization, assume the worst. */ - if (!GetMultiXactInfo(&multixacts, &members, &oldestMultiXactId, &oldestOffset)) - return 0; - - /* If member space utilization is low, no special action is required. */ - if (members <= MULTIXACT_MEMBER_SAFE_THRESHOLD) - return autovacuum_multixact_freeze_max_age; - - /* - * Compute a target for relminmxid advancement. The number of multixacts - * we try to eliminate from the system is based on how far we are past - * MULTIXACT_MEMBER_SAFE_THRESHOLD. - */ - fraction = (double) (members - MULTIXACT_MEMBER_SAFE_THRESHOLD) / - (MULTIXACT_MEMBER_DANGER_THRESHOLD - MULTIXACT_MEMBER_SAFE_THRESHOLD); - victim_multixacts = multixacts * fraction; - - /* fraction could be > 1.0, but lowest possible freeze age is zero */ - if (victim_multixacts > multixacts) - return 0; - result = multixacts - victim_multixacts; - - /* - * Clamp to autovacuum_multixact_freeze_max_age, so that we never make - * autovacuum less aggressive than it would otherwise be. - */ - return Min(result, autovacuum_multixact_freeze_max_age); -} - typedef struct mxtruncinfo { int64 earliestExistingPage; @@ -3159,7 +3006,7 @@ TruncateMultiXact(MultiXactId newOldestMulti, Oid newOldestMultiDB) elog(DEBUG1, "performing multixact truncation: " "offsets [%u, %u), offsets segments [%" PRIx64 ", %" PRIx64 "), " - "members [%u, %u), members segments [%" PRIx64 ", %" PRIx64 ")", + "members [%" PRIu64 ", %" PRIu64 "), members segments [%" PRIx64 ", %" PRIx64 ")", oldestMulti, newOldestMulti, MultiXactIdToOffsetSegment(oldestMulti), MultiXactIdToOffsetSegment(newOldestMulti), @@ -3290,7 +3137,7 @@ MultiXactIdPrecedesOrEquals(MultiXactId multi1, MultiXactId multi2) static bool MultiXactOffsetPrecedes(MultiXactOffset offset1, MultiXactOffset offset2) { - int32 diff = (int32) (offset1 - offset2); + int64 diff = (int64) (offset1 - offset2); return (diff < 0); } @@ -3387,7 +3234,7 @@ multixact_redo(XLogReaderState *record) elog(DEBUG1, "replaying multixact truncation: " "offsets [%u, %u), offsets segments [%" PRIx64 ", %" PRIx64 "), " - "members [%u, %u), members segments [%" PRIx64 ", %" PRIx64 ")", + "members [%" PRIu64 ", %" PRIu64 "), members segments [%" PRIx64 ", %" PRIx64 ")", xlrec.startTruncOff, xlrec.endTruncOff, MultiXactIdToOffsetSegment(xlrec.startTruncOff), MultiXactIdToOffsetSegment(xlrec.endTruncOff), diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c index 3e3c4da01a..3b2b0a522c 100644 --- a/src/backend/access/transam/xlogrecovery.c +++ b/src/backend/access/transam/xlogrecovery.c @@ -885,7 +885,7 @@ InitWalRecovery(ControlFileData *ControlFile, bool *wasShutdown_ptr, U64FromFullTransactionId(checkPoint.nextXid), checkPoint.nextOid))); ereport(DEBUG1, - (errmsg_internal("next MultiXactId: %u; next MultiXactOffset: %u", + (errmsg_internal("next MultiXactId: %u; next MultiXactOffset: %" PRIu64, checkPoint.nextMulti, checkPoint.nextMultiOffset))); ereport(DEBUG1, (errmsg_internal("oldest unfrozen transaction ID: %u, in database %u", diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index ed03e3bd50..259ef60bd3 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -1147,7 +1147,7 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams params, * normally autovacuum_multixact_freeze_max_age, but may be less if we are * short of multixact member space. */ - effective_multixact_freeze_max_age = MultiXactMemberFreezeThreshold(); + effective_multixact_freeze_max_age = autovacuum_multixact_freeze_max_age; /* * Almost ready to set freeze output parameters; check if OldestXmin or diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index 5084af7dfb..26385470c1 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -1151,7 +1151,7 @@ do_start_worker(void) /* Also determine the oldest datminmxid we will consider. */ recentMulti = ReadNextMultiXactId(); - multiForceLimit = recentMulti - MultiXactMemberFreezeThreshold(); + multiForceLimit = recentMulti - autovacuum_multixact_freeze_max_age; if (multiForceLimit < FirstMultiXactId) multiForceLimit -= FirstMultiXactId; @@ -1939,7 +1939,7 @@ do_autovacuum(void) * normally autovacuum_multixact_freeze_max_age, but may be less if we are * short of multixact member space. */ - effective_multixact_freeze_max_age = MultiXactMemberFreezeThreshold(); + effective_multixact_freeze_max_age = autovacuum_multixact_freeze_max_age; /* * Find the pg_database entry and select the default freeze ages. We use diff --git a/src/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.c index 10de058ce9..5295108ade 100644 --- a/src/bin/pg_controldata/pg_controldata.c +++ b/src/bin/pg_controldata/pg_controldata.c @@ -264,7 +264,7 @@ main(int argc, char *argv[]) ControlFile->checkPointCopy.nextOid); printf(_("Latest checkpoint's NextMultiXactId: %u\n"), ControlFile->checkPointCopy.nextMulti); - printf(_("Latest checkpoint's NextMultiOffset: %u\n"), + printf(_("Latest checkpoint's NextMultiOffset: %" PRIu64 "\n"), ControlFile->checkPointCopy.nextMultiOffset); printf(_("Latest checkpoint's oldestXID: %u\n"), ControlFile->checkPointCopy.oldestXid); diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c index a89d72fc5c..4e5eeced89 100644 --- a/src/bin/pg_resetwal/pg_resetwal.c +++ b/src/bin/pg_resetwal/pg_resetwal.c @@ -267,7 +267,7 @@ main(int argc, char *argv[]) case 'O': errno = 0; - set_mxoff = strtoul(optarg, &endptr, 0); + set_mxoff = strtou64(optarg, &endptr, 0); if (endptr == optarg || *endptr != '\0' || errno != 0) { pg_log_error("invalid argument for option %s", "-O"); @@ -743,7 +743,7 @@ PrintControlValues(bool guessed) ControlFile.checkPointCopy.nextOid); printf(_("Latest checkpoint's NextMultiXactId: %u\n"), ControlFile.checkPointCopy.nextMulti); - printf(_("Latest checkpoint's NextMultiOffset: %u\n"), + printf(_("Latest checkpoint's NextMultiOffset: %" PRIu64 "\n"), ControlFile.checkPointCopy.nextMultiOffset); printf(_("Latest checkpoint's oldestXID: %u\n"), ControlFile.checkPointCopy.oldestXid); @@ -817,7 +817,7 @@ PrintNewControlValues(void) if (set_mxoff != -1) { - printf(_("NextMultiOffset: %u\n"), + printf(_("NextMultiOffset: %" PRIu64 "\n"), ControlFile.checkPointCopy.nextMultiOffset); } diff --git a/src/bin/pg_resetwal/t/001_basic.pl b/src/bin/pg_resetwal/t/001_basic.pl index d6bbbd0ced..16b5a62390 100644 --- a/src/bin/pg_resetwal/t/001_basic.pl +++ b/src/bin/pg_resetwal/t/001_basic.pl @@ -213,7 +213,7 @@ push @cmd, sprintf("%d,%d", hex($files[0]) == 0 ? 3 : hex($files[0]), hex($files[-1])); @files = get_slru_files('pg_multixact/offsets'); -$mult = 32 * $blcksz / 4; +$mult = 32 * ($blcksz - 8) / 4; # --multixact-ids argument is "new,old" push @cmd, '--multixact-ids' => sprintf("%d,%d", diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h index 82e4bb90dd..16a0772308 100644 --- a/src/include/access/multixact.h +++ b/src/include/access/multixact.h @@ -28,7 +28,7 @@ #define MultiXactIdIsValid(multi) ((multi) != InvalidMultiXactId) -#define MaxMultiXactOffset ((MultiXactOffset) 0xFFFFFFFF) +#define MaxMultiXactOffset UINT64CONST(0xFFFFFFFFFFFFFFFF) /* * Possible multixact lock modes ("status"). The first four modes are for @@ -147,7 +147,6 @@ extern void MultiXactSetNextMXact(MultiXactId nextMulti, extern void MultiXactAdvanceNextMXact(MultiXactId minMulti, MultiXactOffset minMultiOffset); extern void MultiXactAdvanceOldest(MultiXactId oldestMulti, Oid oldestMultiDB); -extern int MultiXactMemberFreezeThreshold(void); extern void multixact_twophase_recover(FullTransactionId fxid, uint16 info, void *recdata, uint32 len); diff --git a/src/include/c.h b/src/include/c.h index 9ab5e61799..7ab9e68af6 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -666,7 +666,7 @@ typedef uint32 SubTransactionId; /* MultiXactId must be equivalent to TransactionId, to fit in t_xmax */ typedef TransactionId MultiXactId; -typedef uint32 MultiXactOffset; +typedef uint64 MultiXactOffset; typedef uint32 CommandId; -- 2.51.0