On 25 May 2014 17:52, Heikki Linnakangas <hlinnakan...@vmware.com> wrote:
> Here's an idea I tried to explain to Andres and Simon at the pub last night, > on how to reduce the spikes in the amount of WAL written at beginning of a > checkpoint that full-page writes cause. I'm just writing this down for the > sake of the archives; I'm not planning to work on this myself. ... Thanks for that idea, and dinner. It looks useful. I'll call this idea "Background FPWs" > Now, I'm sure there are issues with this scheme I haven't thought about, but > I wanted to get this written down. Note this does not reduce the overall WAL > volume - on the contrary - but it ought to reduce the spike. The requirements we were discussing were around A) reducing WAL volume B) reducing foreground overhead of writing FPWs - which spikes badly after checkpoint and the overhead is paid by the user processes themselves C) need for FPWs during base backup So that gives us a few approaches * Compressing FPWs gives A * Background FPWs gives us B which look like we can combine both ideas * Double-buffering would give us A and B, but not C and would be incompatible with other two ideas Will think some more. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
