From 2ded1f1fbb6e8e2b7927cce93238775604069bc3 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 20 Nov 2020 10:44:09 +1300 Subject: [PATCH] Adjust DSM and DSA slot usage constants (back-patch). 1. Previously, a DSA area would create up to four segments at each size before doubling the size. After this commit, it will create only two at each size, so it ramps up faster and therefore needs fewer slots. 2. Previously, the total limit on DSM slots allowed for 2 per connection. Switch to 5 per connection. This back-patches commit d061ea21 from release 13 into 10-12 based on a field complaint. Discussion: https://postgr.es/m/CAO03teA%2BjE1qt5iWDWzHqaufqBsF6EoOgZphnazps_tr_jDPZA%40mail.gmail.com Discussion: https://postgr.es/m/CA%2BhUKGL6H2BpGbiF7Lj6QiTjTGyTLW_vLR%3DSn2tEBeTcYXiMKw%40mail.gmail.com --- src/backend/storage/ipc/dsm.c | 7 +------ src/backend/utils/mmgr/dsa.c | 2 +- 2 files changed, 2 insertions(+), 7 deletions(-) diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c index 9bf16de940..40a1e46fc0 100644 --- a/src/backend/storage/ipc/dsm.c +++ b/src/backend/storage/ipc/dsm.c @@ -45,13 +45,8 @@ #define PG_DYNSHMEM_CONTROL_MAGIC 0x9a503d32 -/* - * There's no point in getting too cheap here, because the minimum allocation - * is one OS page, which is probably at least 4KB and could easily be as high - * as 64KB. Each currently sizeof(dsm_control_item), currently 8 bytes. - */ #define PG_DYNSHMEM_FIXED_SLOTS 64 -#define PG_DYNSHMEM_SLOTS_PER_BACKEND 2 +#define PG_DYNSHMEM_SLOTS_PER_BACKEND 5 #define INVALID_CONTROL_SLOT ((uint32) -1) diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c index 900cd8357c..5a53c8290a 100644 --- a/src/backend/utils/mmgr/dsa.c +++ b/src/backend/utils/mmgr/dsa.c @@ -74,7 +74,7 @@ * dsm.c's limits on total number of segments), or limiting the total size * an area can manage when using small pointers. */ -#define DSA_NUM_SEGMENTS_AT_EACH_SIZE 4 +#define DSA_NUM_SEGMENTS_AT_EACH_SIZE 2 /* * The number of bits used to represent the offset part of a dsa_pointer.