On Wed, Jan 20, 2016 at 9:07 PM, Andres Freund <andres@anarazel.de> wrote: > > On 2016-01-20 12:16:24 -0300, Alvaro Herrera wrote: > > Andres Freund wrote: > > > > > The relevant thread is at > > > http://archives.postgresql.org/message-id/CA%2BTgmoaCr3kDPafK5ygYDA9mF9zhObGp_13q0XwkEWsScw6h%3Dw%40mail.gmail.com > > > what I didn't remember is that I voiced concern back then about exactly this: > > > http://archives.postgresql.org/message-id/201112011518.29964.andres%40anarazel.de > > > ;) > > > > Interesting. If we consider for a minute that part of the cause for the > > slowdown is slowness in pg_clog, maybe we should reconsider the initial > > decision to flush as quickly as possible (i.e. adopt a strategy where > > walwriter sleeps a bit between two flushes) in light of the group-update > > feature for CLOG being proposed by Amit Kapila in another thread -- it > > seems that these things might go hand-in-hand. > > I don't think it's strongly related - the contention here is on read > access to the clog, not on write access.
Aren't reads on clog contended with parallel writes to clog?