diff options
Diffstat (limited to 'src/backend/storage/ipc/sinval.c')
| -rw-r--r-- | src/backend/storage/ipc/sinval.c | 53 |
1 files changed, 47 insertions, 6 deletions
diff --git a/src/backend/storage/ipc/sinval.c b/src/backend/storage/ipc/sinval.c index 2907fca1a1e..44b8d116255 100644 --- a/src/backend/storage/ipc/sinval.c +++ b/src/backend/storage/ipc/sinval.c @@ -8,16 +8,14 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.25 2001/01/24 19:43:07 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.26 2001/02/26 00:50:07 tgl Exp $ * *------------------------------------------------------------------------- */ -/* #define INVALIDDEBUG 1 */ +#include "postgres.h" #include <sys/types.h> -#include "postgres.h" - #include "storage/backendid.h" #include "storage/proc.h" #include "storage/sinval.h" @@ -348,10 +346,53 @@ GetSnapshotData(bool serializable) } /* - * GetUndoRecPtr -- returns oldest PROC->logRec. + * CountActiveBackends --- count backends (other than myself) that are in + * active transactions. This is used as a heuristic to decide if + * a pre-XLOG-flush delay is worthwhile during commit. + * + * An active transaction is something that has written at least one XLOG + * record; read-only transactions don't count. Also, do not count backends + * that are blocked waiting for locks, since they are not going to get to + * run until someone else commits. */ -XLogRecPtr GetUndoRecPtr(void); +int +CountActiveBackends(void) +{ + SISeg *segP = shmInvalBuffer; + ProcState *stateP = segP->procState; + int count = 0; + int index; + /* + * Note: for speed, we don't acquire SInvalLock. This is a little bit + * bogus, but since we are only testing xrecoff for zero or nonzero, + * it should be OK. The result is only used for heuristic purposes + * anyway... + */ + for (index = 0; index < segP->lastBackend; index++) + { + SHMEM_OFFSET pOffset = stateP[index].procStruct; + + if (pOffset != INVALID_OFFSET) + { + PROC *proc = (PROC *) MAKE_PTR(pOffset); + + if (proc == MyProc) + continue; /* do not count myself */ + if (proc->logRec.xrecoff == 0) + continue; /* do not count if not in a transaction */ + if (proc->waitLock != NULL) + continue; /* do not count if blocked on a lock */ + count++; + } + } + + return count; +} + +/* + * GetUndoRecPtr -- returns oldest PROC->logRec. + */ XLogRecPtr GetUndoRecPtr(void) { |