From 77ec7a6a192e227899c80a873c4479c866024587 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 19 Mar 2021 13:06:35 +1300 Subject: [PATCH v6 2/3] Provide recovery_init_sync_method=none. Although it's rife with hazards and not a good option to use in general, some expert users may want to be able to disable the initial sync performed before crash recovery. Explicitly discouraged in the documentation. Discussion https://postgr.es/m/11bc2bb7-ecb5-3ad0-b39f-df632734cd81%40discourse.org --- doc/src/sgml/config.sgml | 9 +++++++++ src/backend/storage/file/fd.c | 9 +++++++-- src/backend/utils/misc/guc.c | 1 + src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/storage/fd.h | 3 ++- 5 files changed, 20 insertions(+), 4 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 32de8235bf..0d058de261 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -9748,6 +9748,15 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir' PostgreSQL, and relevant error messages may appear only in kernel logs. + + The option none can be specified to skip this step. + This is only safe if all buffered data is known to have been flushed + to disk already, for example by a tool such as + pg_basebackup without + --no-sync. It is not a good idea to + leave this option configured permanently in general, as it will + affect future crash recovery cycles. + diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c index 28933f8bbe..b59fbc4cfe 100644 --- a/src/backend/storage/file/fd.c +++ b/src/backend/storage/file/fd.c @@ -3293,8 +3293,9 @@ do_syncfs(const char *path) #endif /* - * Issue fsync recursively on PGDATA and all its contents, or issue syncfs for - * all potential filesystem, depending on recovery_init_sync_method setting. + * Issue fsync recursively on PGDATA and all its contents, issue syncfs for all + * potential filesystem, or do nothing, depending on the + * recovery_init_sync_method setting. * * We fsync regular files and directories wherever they are, but we * follow symlinks only for pg_wal and immediately under pg_tblspc. @@ -3323,6 +3324,10 @@ SyncDataDirectory(void) if (!enableFsync) return; + /* Likewise if this specific sync step is disabled. */ + if (recovery_init_sync_method == RECOVERY_INIT_SYNC_METHOD_NONE) + return; + /* * If pg_wal is a symlink, we'll need to recurse into it separately, * because the first walkdir below will ignore it. diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 8679063e5f..4fa67a5160 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -492,6 +492,7 @@ static struct config_enum_entry recovery_init_sync_method_options[] = { #ifdef HAVE_SYNCFS {"syncfs", RECOVERY_INIT_SYNC_METHOD_SYNCFS, false}, #endif + {"none", RECOVERY_INIT_SYNC_METHOD_NONE, false}, {NULL, 0, false} }; diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 76b9e815a2..8b1610f6ec 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -760,7 +760,7 @@ #restart_after_crash = on # reinitialize after backend crash? #remove_temp_files_after_crash = on # remove temporary files after # backend crash? -#recovery_init_sync_method = fsync # fsync, syncfs (Linux 5.8+) +#recovery_init_sync_method = fsync # fsync, syncfs (Linux 5.8+), none #data_sync_retry = off # retry or panic on failure to fsync # data? # (change requires restart) diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h index 328473bdc9..dca44c38c4 100644 --- a/src/include/storage/fd.h +++ b/src/include/storage/fd.h @@ -47,7 +47,8 @@ typedef enum RecoveryInitSyncMethod { RECOVERY_INIT_SYNC_METHOD_FSYNC, - RECOVERY_INIT_SYNC_METHOD_SYNCFS + RECOVERY_INIT_SYNC_METHOD_SYNCFS, + RECOVERY_INIT_SYNC_METHOD_NONE } RecoveryInitSyncMethod; struct iovec; /* avoid including port/pg_iovec.h here */ -- 2.30.1