Thomas, 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.
Thanks again, Jerry On Thu, Jun 21, 2018 at 10:20 PM, Thomas Munro < thomas.mu...@enterprisedb.com> wrote: > On Fri, Jun 22, 2018 at 11:22 AM, David Pacheco <d...@joyent.com> wrote: > > On Wed, Jun 20, 2018 at 10:35 AM, Jerry Jelinek < > jerry.jeli...@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 >
