On Fri, Jun 22, 2018 at 11:22 AM, David Pacheco <dap@xxxxxxxxxx> wrote: > On Wed, Jun 20, 2018 at 10:35 AM, Jerry Jelinek <jerry.jelinek@xxxxxxxxxx> > wrote: >> I have implemented a small change to allow WAL recycling to be disabled. >> It is visible at: >> https://cr.joyent.us/#/c/4263/ >> >> I'd appreciate getting any feedback on this. >> tl;dr: We've found that under many conditions, PostgreSQL's re-use of old >> WAL files appears to significantly degrade query latency on ZFS. I haven't tested by it looks reasonable to me. It needs documentation in doc/src/sgml/config.sgml. It should be listed in src/backend/utils/misc/postgresql.conf.sample. We'd want a patch against our master branch. Could you please register it in commitfest.postgresql.org so we don't lose track of it? Hey, a question about PostgreSQL on ZFS: what do you guys think about pg_flush_data() in fd.c? It does mmap(), msync(), munmap() to try to influence writeback? I wonder if at least on some operating systems that schlepps a bunch of data out of ZFS ARC into OS page cache, kinda trashing the latter? -- Thomas Munro http://www.enterprisedb.com
