On Tue, Aug 23, 2016 at 10:50 PM, Amit Kapila <amit.kapil...@gmail.com> wrote: > On Tue, Aug 23, 2016 at 6:11 PM, Michael Paquier > <michael.paqu...@gmail.com> wrote: >> On Tue, Aug 23, 2016 at 8:02 PM, Masahiko Sawada <sawada.m...@gmail.com> >> wrote: >>> As for PoC, I implemented parallel vacuum so that each worker >>> processes both 1 and 2 phases for particular block range. >>> Suppose we vacuum 1000 blocks table with 4 workers, each worker >>> processes 250 consecutive blocks in phase 1 and then reclaims dead >>> tuples from heap and indexes (phase 2). >> >> So each worker is assigned a range of blocks, and processes them in >> parallel? This does not sound performance-wise. I recall Robert and >> Amit emails on the matter for sequential scan that this would suck >> performance out particularly for rotating disks. >> > > The implementation in patch is same as we have initially thought for > sequential scan, but turned out that it is not good way to do because > it can lead to inappropriate balance of work among workers. Suppose > one worker is able to finish it's work, it won't be able to do more.
Ah, so it was the reason. Thanks for confirming my doubts on what is proposed. -- Michael -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
