From 8fd2a0611a13ca40fe7d4c28a27257ba0f7e2a7a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?C=C3=A9dric=20Villemain?= Date: Wed, 3 Jan 2024 19:08:37 +0100 Subject: [PATCH 2/3] Allow pg_prewarm to use new smgrprefetch range This commit replaces BufferPrefetch with smgrprefetch (with range). It reduces the number of instructions to prefetch data. I also defined a PREWARM_PREFETCH_RANGE which is by default the size of a segment so there is a chance to interrupt the prefetching (on very large table it might be desirable). --- contrib/pg_prewarm/pg_prewarm.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/contrib/pg_prewarm/pg_prewarm.c b/contrib/pg_prewarm/pg_prewarm.c index 1de1b39482..aea07927db 100644 --- a/contrib/pg_prewarm/pg_prewarm.c +++ b/contrib/pg_prewarm/pg_prewarm.c @@ -25,6 +25,8 @@ #include "utils/lsyscache.h" #include "utils/rel.h" +#define PREWARM_PREFETCH_RANGE RELSEG_SIZE + PG_MODULE_MAGIC; PG_FUNCTION_INFO_V1(pg_prewarm); @@ -156,11 +158,21 @@ pg_prewarm(PG_FUNCTION_ARGS) * no practical way to do that at present without a gross modularity * violation, so we just do this. */ - for (block = first_block; block <= last_block; ++block) + for (block = first_block; block <= last_block; + block += PREWARM_PREFETCH_RANGE) { + int seek = Min(PREWARM_PREFETCH_RANGE, (last_block - block + 1)); + + /* + * if handling a multi-TB relation, we need a way to interrupt the + * prefetching: smgrprefetch (mdprefetch) will loop on all segments + * without interruption so we use a range and keep the following + * CHECK in place + */ CHECK_FOR_INTERRUPTS(); - PrefetchBuffer(rel, forkNumber, block); - ++blocks_done; + + smgrprefetch(RelationGetSmgr(rel), forkNumber, block, seek); + blocks_done += seek; } #else ereport(ERROR, -- 2.39.2