From 674f54c720bfd7d56de04370e5a015fe929c6b65 Mon Sep 17 00:00:00 2001 From: Nathan Bossart Date: Sun, 5 Dec 2021 22:02:40 -0800 Subject: [PATCH v13 5/6] Move removal of old serialized snapshots to custodian. This was only done during checkpoints because it was a convenient place to put it. However, if there are many snapshots to remove, it can significantly extend checkpoint time. To avoid this, move this work to the newly-introduced custodian process. --- src/backend/access/transam/xlog.c | 8 ++++++-- src/backend/postmaster/custodian.c | 2 ++ src/backend/replication/logical/snapbuild.c | 9 ++++----- src/include/postmaster/custodian.h | 1 + src/include/replication/snapbuild.h | 2 +- 5 files changed, 14 insertions(+), 8 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index a31fbbff78..4991c10f86 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -76,12 +76,12 @@ #include "port/atomics.h" #include "port/pg_iovec.h" #include "postmaster/bgwriter.h" +#include "postmaster/custodian.h" #include "postmaster/startup.h" #include "postmaster/walwriter.h" #include "replication/logical.h" #include "replication/origin.h" #include "replication/slot.h" -#include "replication/snapbuild.h" #include "replication/walreceiver.h" #include "replication/walsender.h" #include "storage/bufmgr.h" @@ -7001,10 +7001,14 @@ CheckPointGuts(XLogRecPtr checkPointRedo, int flags) { CheckPointRelationMap(); CheckPointReplicationSlots(); - CheckPointSnapBuild(); CheckPointLogicalRewriteHeap(); CheckPointReplicationOrigin(); + /* tasks offloaded to custodian */ + RequestCustodian(CUSTODIAN_REMOVE_SERIALIZED_SNAPSHOTS, + !IsUnderPostmaster, + (Datum) 0); + /* Write out all dirty data in SLRUs and the main buffer pool */ TRACE_POSTGRESQL_BUFFER_CHECKPOINT_START(flags); CheckpointStats.ckpt_write_t = GetCurrentTimestamp(); diff --git a/src/backend/postmaster/custodian.c b/src/backend/postmaster/custodian.c index fe1f48844e..855a756ca0 100644 --- a/src/backend/postmaster/custodian.c +++ b/src/backend/postmaster/custodian.c @@ -25,6 +25,7 @@ #include "pgstat.h" #include "postmaster/custodian.h" #include "postmaster/interrupt.h" +#include "replication/snapbuild.h" #include "storage/bufmgr.h" #include "storage/condition_variable.h" #include "storage/fd.h" @@ -71,6 +72,7 @@ struct cust_task_funcs_entry */ static const struct cust_task_funcs_entry cust_task_functions[] = { {CUSTODIAN_REMOVE_TEMP_FILES, RemovePgTempFiles, NULL}, + {CUSTODIAN_REMOVE_SERIALIZED_SNAPSHOTS, RemoveOldSerializedSnapshots, NULL}, {INVALID_CUSTODIAN_TASK, NULL, NULL} /* must be last */ }; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index a1fd1d92d6..f957b9aa49 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -2037,14 +2037,13 @@ SnapBuildRestoreContents(int fd, char *dest, Size size, const char *path) /* * Remove all serialized snapshots that are not required anymore because no - * slot can need them. This doesn't actually have to run during a checkpoint, - * but it's a convenient point to schedule this. + * slot can need them. * - * NB: We run this during checkpoints even if logical decoding is disabled so - * we cleanup old slots at some point after it got disabled. + * NB: We run this even if logical decoding is disabled so we cleanup old slots + * at some point after it got disabled. */ void -CheckPointSnapBuild(void) +RemoveOldSerializedSnapshots(void) { XLogRecPtr cutoff; XLogRecPtr redo; diff --git a/src/include/postmaster/custodian.h b/src/include/postmaster/custodian.h index 80890ceadd..37334941cc 100644 --- a/src/include/postmaster/custodian.h +++ b/src/include/postmaster/custodian.h @@ -19,6 +19,7 @@ typedef enum CustodianTask { CUSTODIAN_REMOVE_TEMP_FILES, + CUSTODIAN_REMOVE_SERIALIZED_SNAPSHOTS, NUM_CUSTODIAN_TASKS, /* new tasks go above */ INVALID_CUSTODIAN_TASK diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index 2a697e57c3..9eba403e0c 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -57,7 +57,7 @@ struct ReorderBuffer; struct xl_heap_new_cid; struct xl_running_xacts; -extern void CheckPointSnapBuild(void); +extern void RemoveOldSerializedSnapshots(void); extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *reorder, TransactionId xmin_horizon, XLogRecPtr start_lsn, -- 2.25.1