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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/storage/buffer/bufmgr.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/storage/buffer/bufmgr.c')
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 79ca9d18d07..d04afa5ab9c 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -160,9 +160,12 @@ int maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY; /* * Limit on how many blocks should be handled in single I/O operations. * StartReadBuffers() callers should respect it, as should other operations - * that call smgr APIs directly. + * that call smgr APIs directly. It is computed as the minimum of underlying + * GUCs io_combine_limit_guc and io_max_combine_limit. */ int io_combine_limit = DEFAULT_IO_COMBINE_LIMIT; +int io_combine_limit_guc = DEFAULT_IO_COMBINE_LIMIT; +int io_max_combine_limit = DEFAULT_IO_COMBINE_LIMIT; /* * GUC variables about triggering kernel writeback for buffers written; OS |