From fc0acf43878bcd70dc1b701b054521d8553d2088 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 1 Oct 2014 16:37:15 +0300 Subject: [PATCH] Remove num_xloginsert_locks GUC, replace with a #define I left the GUC in place for the beta period, so that people could experiment with different values. No-one's come up with any data that a different value would be better under some circumstances, so rather than try to document to users what the GUC, let's just hard-code the current value, 8. --- src/backend/access/transam/xlog.c | 34 ++++++++++++++++++------------- src/backend/utils/misc/guc.c | 11 ---------- src/include/access/xlog.h | 1 - 3 files changed, 20 insertions(+), 26 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9b938bda74..cfa4e3a00f 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -90,12 +90,18 @@ int sync_method = DEFAULT_SYNC_METHOD; int wal_level = WAL_LEVEL_MINIMAL; int CommitDelay = 0; /* precommit delay in microseconds */ int CommitSiblings = 5; /* # concurrent xacts needed to sleep */ -int num_xloginsert_locks = 8; #ifdef WAL_DEBUG bool XLOG_DEBUG = false; #endif +/* + * Number of WAL insertion locks to use. A higher value allows more insertions + * to happen concurrently, but adds some CPU overhead to flushing the WAL, + * which needs to iterate all the locks. + */ +#define NUM_XLOGINSERT_LOCKS 8 + /* * XLOGfileslop is the maximum number of preallocated future XLOG segments. * When we are done with an old XLOG segment file, we will recycle it as a @@ -1089,9 +1095,9 @@ begin:; * inserter acquires an insertion lock. In addition to just indicating that * an insertion is in progress, the lock tells others how far the inserter * has progressed. There is a small fixed number of insertion locks, - * determined by the num_xloginsert_locks GUC. When an inserter crosses a - * page boundary, it updates the value stored in the lock to the how far it - * has inserted, to allow the previous buffer to be flushed. + * determined by NUM_XLOGINSERT_LOCKS. When an inserter crosses a page + * boundary, it updates the value stored in the lock to the how far it has + * inserted, to allow the previous buffer to be flushed. * * Holding onto an insertion lock also protects RedoRecPtr and * fullPageWrites from changing until the insertion is finished. @@ -1572,7 +1578,7 @@ WALInsertLockAcquire(void) static int lockToTry = -1; if (lockToTry == -1) - lockToTry = MyProc->pgprocno % num_xloginsert_locks; + lockToTry = MyProc->pgprocno % NUM_XLOGINSERT_LOCKS; MyLockNo = lockToTry; /* @@ -1592,7 +1598,7 @@ WALInsertLockAcquire(void) * than locks, it still helps to distribute the inserters evenly * across the locks. */ - lockToTry = (lockToTry + 1) % num_xloginsert_locks; + lockToTry = (lockToTry + 1) % NUM_XLOGINSERT_LOCKS; } } @@ -1611,7 +1617,7 @@ WALInsertLockAcquireExclusive(void) * than any real XLogRecPtr value, to make sure that no-one blocks waiting * on those. */ - for (i = 0; i < num_xloginsert_locks - 1; i++) + for (i = 0; i < NUM_XLOGINSERT_LOCKS - 1; i++) { LWLockAcquireWithVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, @@ -1634,7 +1640,7 @@ WALInsertLockRelease(void) { int i; - for (i = 0; i < num_xloginsert_locks; i++) + for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) LWLockRelease(&WALInsertLocks[i].l.lock); holdingAllLocks = false; @@ -1658,8 +1664,8 @@ WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt) * We use the last lock to mark our actual position, see comments in * WALInsertLockAcquireExclusive. */ - LWLockUpdateVar(&WALInsertLocks[num_xloginsert_locks - 1].l.lock, - &WALInsertLocks[num_xloginsert_locks - 1].l.insertingAt, + LWLockUpdateVar(&WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.lock, + &WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.insertingAt, insertingAt); } else @@ -1726,7 +1732,7 @@ WaitXLogInsertionsToFinish(XLogRecPtr upto) * out for any insertion that's still in progress. */ finishedUpto = reservedUpto; - for (i = 0; i < num_xloginsert_locks; i++) + for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { XLogRecPtr insertingat = InvalidXLogRecPtr; @@ -4781,7 +4787,7 @@ XLOGShmemSize(void) size = sizeof(XLogCtlData); /* WAL insertion locks, plus alignment */ - size = add_size(size, mul_size(sizeof(WALInsertLockPadded), num_xloginsert_locks + 1)); + size = add_size(size, mul_size(sizeof(WALInsertLockPadded), NUM_XLOGINSERT_LOCKS + 1)); /* xlblocks array */ size = add_size(size, mul_size(sizeof(XLogRecPtr), XLOGbuffers)); /* extra alignment padding for XLOG I/O buffers */ @@ -4840,7 +4846,7 @@ XLOGShmemInit(void) ((uintptr_t) allocptr) %sizeof(WALInsertLockPadded); WALInsertLocks = XLogCtl->Insert.WALInsertLocks = (WALInsertLockPadded *) allocptr; - allocptr += sizeof(WALInsertLockPadded) * num_xloginsert_locks; + allocptr += sizeof(WALInsertLockPadded) * NUM_XLOGINSERT_LOCKS; XLogCtl->Insert.WALInsertLockTrancheId = LWLockNewTrancheId(); @@ -4849,7 +4855,7 @@ XLOGShmemInit(void) XLogCtl->Insert.WALInsertLockTranche.array_stride = sizeof(WALInsertLockPadded); LWLockRegisterTranche(XLogCtl->Insert.WALInsertLockTrancheId, &XLogCtl->Insert.WALInsertLockTranche); - for (i = 0; i < num_xloginsert_locks; i++) + for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { LWLockInitialize(&WALInsertLocks[i].l.lock, XLogCtl->Insert.WALInsertLockTrancheId); diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 21f283bc4b..ea58cf6e50 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -2119,17 +2119,6 @@ static struct config_int ConfigureNamesInt[] = NULL, NULL, NULL }, - { - {"xloginsert_locks", PGC_POSTMASTER, WAL_SETTINGS, - gettext_noop("Sets the number of locks used for concurrent xlog insertions."), - NULL, - GUC_NOT_IN_SAMPLE - }, - &num_xloginsert_locks, - 8, 1, 1000, - NULL, NULL, NULL - }, - { /* see max_connections */ {"max_wal_senders", PGC_POSTMASTER, REPLICATION_SENDING, diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index 1eaa5c1c21..86a1c40d2a 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -192,7 +192,6 @@ extern bool EnableHotStandby; extern bool fullPageWrites; extern bool wal_log_hints; extern bool log_checkpoints; -extern int num_xloginsert_locks; /* WAL levels */ typedef enum WalLevel -- 2.40.0