On 2020-Aug-25, Jakub Wartak wrote: > Turning on/off the defer SLRU patch and/or fsync doesn't seem to make > any difference, so if anyone is curious the next sets of append-only > bottlenecks is like below: > > 14.69% postgres postgres [.] hash_search_with_hash_value > ---hash_search_with_hash_value > |--9.80%--BufTableLookup > | ReadBuffer_common > | ReadBufferWithoutRelcache > | XLogReadBufferExtended > | XLogReadBufferForRedoExtended > | |--7.76%--btree_xlog_insert > | | btree_redo > | | StartupXLOG > | --1.63%--heap_xlog_insert > --4.90%--smgropen > |--2.86%--ReadBufferWithoutRelcache
Looking at an earlier report of this problem I was thinking whether it'd make sense to replace SMgrRelationHash with a simplehash table; I have a half-written patch for that, but I haven't completed that work. However, in the older profile things were looking different, as hash_search_with_hash_value was taking 35.25%, and smgropen was 33.74% of it. BufTableLookup was also there but only 1.51%. So I'm not so sure now that that'll pay off as clearly as I had hoped. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
