From a098871d02b4883bfa531cb6e20ab4b66a6b80e0 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 1 Sep 2017 22:39:35 +1200 Subject: [PATCH] Remove obsolete SLRU wrapping and warnings from predicate.c. When SSI was developed slru.c was limited to segments files with names in the range 0000..FFFF. This didn't allow enough space for predicate.c to store every possible xid when spilling old transactions to disk, so it would wrap around sooner and print warnings. Since commits 638cf09e and 73c986ad increased the number of segments files slru.c could manage, that behavior is unnecessary. Therefore remove that code. Author: Thomas Munro Reviewed-By: Anastasia Lubennikova Discussion: https://postgr.es/m/CAEepm=3XfsTSxgEbEOmxu0QDiXy0o18NUg2nC89JZcCGE+XFPA@mail.gmail.com --- src/backend/storage/lmgr/predicate.c | 51 +++--------------------------------- 1 file changed, 3 insertions(+), 48 deletions(-) diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 6a6d9d6d5cc..5d4374cb06f 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -318,11 +318,9 @@ static SlruCtlData OldSerXidSlruCtlData; #define OLDSERXID_ENTRIESPERPAGE (OLDSERXID_PAGESIZE / OLDSERXID_ENTRYSIZE) /* - * Set maximum pages based on the lesser of the number needed to track all - * transactions and the maximum that SLRU supports. + * Set maximum pages based on the number needed to track all transactions. */ -#define OLDSERXID_MAX_PAGE Min(SLRU_PAGES_PER_SEGMENT * 0x10000 - 1, \ - (MaxTransactionId) / OLDSERXID_ENTRIESPERPAGE) +#define OLDSERXID_MAX_PAGE ((MaxTransactionId) / OLDSERXID_ENTRIESPERPAGE) #define OldSerXidNextPage(page) (((page) >= OLDSERXID_MAX_PAGE) ? 0 : (page) + 1) @@ -330,7 +328,7 @@ static SlruCtlData OldSerXidSlruCtlData; (OldSerXidSlruCtl->shared->page_buffer[slotno] + \ ((((uint32) (xid)) % OLDSERXID_ENTRIESPERPAGE) * OLDSERXID_ENTRYSIZE)))) -#define OldSerXidPage(xid) ((((uint32) (xid)) / OLDSERXID_ENTRIESPERPAGE) % (OLDSERXID_MAX_PAGE + 1)) +#define OldSerXidPage(xid) (((uint32) (xid)) / OLDSERXID_ENTRIESPERPAGE) #define OldSerXidSegment(page) ((page) / SLRU_PAGES_PER_SEGMENT) typedef struct OldSerXidControlData @@ -338,7 +336,6 @@ typedef struct OldSerXidControlData int headPage; /* newest initialized page */ TransactionId headXid; /* newest valid Xid in the SLRU */ TransactionId tailXid; /* oldest xmin we might be interested in */ - bool warningIssued; /* have we issued SLRU wrap-around warning? */ } OldSerXidControlData; typedef struct OldSerXidControlData *OldSerXidControl; @@ -826,7 +823,6 @@ OldSerXidInit(void) oldSerXidControl->headPage = -1; oldSerXidControl->headXid = InvalidTransactionId; oldSerXidControl->tailXid = InvalidTransactionId; - oldSerXidControl->warningIssued = false; } } @@ -882,47 +878,6 @@ OldSerXidAdd(TransactionId xid, SerCommitSeqNo minConflictCommitSeqNo) if (isNewPage) oldSerXidControl->headPage = targetPage; - /* - * Give a warning if we're about to run out of SLRU pages. - * - * slru.c has a maximum of 64k segments, with 32 (SLRU_PAGES_PER_SEGMENT) - * pages each. We need to store a 64-bit integer for each Xid, and with - * default 8k block size, 65536*32 pages is only enough to cover 2^30 - * XIDs. If we're about to hit that limit and wrap around, warn the user. - * - * To avoid spamming the user, we only give one warning when we've used 1 - * billion XIDs, and stay silent until the situation is fixed and the - * number of XIDs used falls below 800 million again. - * - * XXX: We have no safeguard to actually *prevent* the wrap-around, - * though. All you get is a warning. - */ - if (oldSerXidControl->warningIssued) - { - TransactionId lowWatermark; - - lowWatermark = tailXid + 800000000; - if (lowWatermark < FirstNormalTransactionId) - lowWatermark = FirstNormalTransactionId; - if (TransactionIdPrecedes(xid, lowWatermark)) - oldSerXidControl->warningIssued = false; - } - else - { - TransactionId highWatermark; - - highWatermark = tailXid + 1000000000; - if (highWatermark < FirstNormalTransactionId) - highWatermark = FirstNormalTransactionId; - if (TransactionIdFollows(xid, highWatermark)) - { - oldSerXidControl->warningIssued = true; - ereport(WARNING, - (errmsg("memory for serializable conflict tracking is nearly exhausted"), - errhint("There might be an idle transaction or a forgotten prepared transaction causing this."))); - } - } - if (isNewPage) { /* Initialize intervening pages. */ -- 2.13.2