Thanks for taking a look at this. I'll work on getting a patch together for the master branch. I'll also take a look at the other question you raised and get back to you once I have more information.
On Fri, Jun 22, 2018 at 11:22 AM, David Pacheco <dap@joyent.com> wrote: > On Wed, Jun 20, 2018 at 10:35 AM, Jerry Jelinek <jerry.jelinek@joyent.com> > 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
