On 2016-04-16 17:52:44 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > On 2016-04-16 16:44:52 -0400, Noah Misch wrote: > >> That is more controversial than the potential ~2% regression for > >> old_snapshot_threshold=-1. Alvaro[2] and Robert[3] are okay releasing > >> that way, and Andres[4] is not. > > > FWIW, I could be kinda convinced that it's temporarily ok, if there'd be > > a clear proposal on the table how to solve the scalability issue around > > MaintainOldSnapshotTimeMapping(). Postponing the optimization around > > something as trivial as a spinlock around reading an LSN is one thing, > > postponing something we don't know the solution to is anohter. > > The message Noah cited mentions only a 4% regression, but this one > seems far worse: > > http://www.postgresql.org/message-id/20160413200148.bawmwjdmggbll...@alap3.anarazel.de > > That's more than a 5X penalty, which seems like it would make the > feature unusable; unless there is an argument that that's an extreme > case that wouldn't be representative of most real-world usage. > Which there may well be; I've not been following this thread carefully.
The 4 % was with the feature disabled (in comparison to before it's introduction), we're not sure where that's coming from. But the 5x - and that was just on a mid-sized box - is with the feature enabled. - Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers