Re: Displaying accumulated autovacuum cost

Attached patch includes "math is hard" reworking, so it displays the 
average write rate in the log output automatically:

LOG:  automatic vacuum of table "pgbench.public.pgbench_accounts": index 
scans: 1
     pages: 0 removed, 163935 remain
     tuples: 2000000 removed, 4625165 remain
     buffer usage: 111901 hits, 123348 misses, 102351 dirtied, 23.365 
MiB/s write rate
     system usage: CPU 1.84s/4.22u sec elapsed 34.22 sec

All of the updates to the process title are gone, in favor of some 
progress report mechanism TBD.  The summary is much more important than 
the progress tracking part as far as I'm concerned, I don't mind 
splitting things apart to try and get this part in earlier.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us