From 10f6646847515b1ab02735c24b04abaf1996f65f Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Wed, 19 Mar 2025 11:40:56 +1300 Subject: 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 (earlier version) Discussion: https://postgr.es/m/CA%2BhUKG%2B2T9p-%2BzM6Eeou-RAJjTML6eit1qn26f9twznX59qtCA%40mail.gmail.com --- src/include/utils/guc_hooks.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'src/include/utils/guc_hooks.h') diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h index a3eba8fbe21..0f1e74f96c9 100644 --- a/src/include/utils/guc_hooks.h +++ b/src/include/utils/guc_hooks.h @@ -86,6 +86,8 @@ extern const char *show_log_timezone(void); extern bool check_maintenance_io_concurrency(int *newval, void **extra, GucSource source); extern void assign_maintenance_io_concurrency(int newval, void *extra); +extern void assign_io_max_combine_limit(int newval, void *extra); +extern void assign_io_combine_limit(int newval, void *extra); extern bool check_max_slot_wal_keep_size(int *newval, void **extra, GucSource source); extern void assign_max_wal_size(int newval, void *extra); -- cgit v1.2.3