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| author | Thomas Munro <tmunro@postgresql.org> | 2025-03-19 11:40:56 +1300 |
|---|---|---|
| committer | Thomas Munro <tmunro@postgresql.org> | 2025-03-19 15:23:54 +1300 |
| commit | 10f6646847515b1ab02735c24b04abaf1996f65f (patch) | |
| tree | e49ca63aec12d99997f4fa91a6d4e3a11dbbe858 /src/backend/utils/misc/guc_tables.c | |
| parent | 17d8bba6dad12e14a7cafca9ef5eef21e577e9c3 (diff) | |
| download | postgresql-10f6646847515b1ab02735c24b04abaf1996f65f.tar.gz postgresql-10f6646847515b1ab02735c24b04abaf1996f65f.zip | |
Introduce io_max_combine_limit.
The existing io_combine_limit can be changed by users. The new
io_max_combine_limit is fixed at server startup time, and functions as a
silent clamp on the user setting. That in itself is probably quite
useful, but the primary motivation is:
aio_init.c allocates shared memory for all asynchronous IOs including
some per-block data, and we didn't want to waste memory you'd never used
by assuming they could be up to PG_IOV_MAX. This commit already halves
the size of 'AioHandleIov' and 'AioHandleData'. A follow-up commit can
now expand PG_IOV_MAX without affecting that.
Since our GUC system doesn't support dependencies or cross-checks
between GUCs, the user-settable one now assigns a "raw" value to
io_combine_limit_guc, and the lower of io_combine_limit_guc and
io_max_combine_limit is maintained in io_combine_limit.
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier version)
Discussion: https://postgr.es/m/CA%2BhUKG%2B2T9p-%2BzM6Eeou-RAJjTML6eit1qn26f9twznX59qtCA%40mail.gmail.com
Diffstat (limited to 'src/backend/utils/misc/guc_tables.c')
| -rw-r--r-- | src/backend/utils/misc/guc_tables.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index 60a40ed445a..ead80257192 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -3253,6 +3253,20 @@ struct config_int ConfigureNamesInt[] = }, { + {"io_max_combine_limit", + PGC_POSTMASTER, + RESOURCES_IO, + gettext_noop("Server-wide limit that clamps io_combine_limit."), + NULL, + GUC_UNIT_BLOCKS + }, + &io_max_combine_limit, + DEFAULT_IO_COMBINE_LIMIT, + 1, MAX_IO_COMBINE_LIMIT, + NULL, assign_io_max_combine_limit, NULL + }, + + { {"io_combine_limit", PGC_USERSET, RESOURCES_IO, @@ -3263,7 +3277,7 @@ struct config_int ConfigureNamesInt[] = &io_combine_limit, DEFAULT_IO_COMBINE_LIMIT, 1, MAX_IO_COMBINE_LIMIT, - NULL, NULL, NULL + NULL, assign_io_combine_limit, NULL }, { |