pgsql: Improve logging of autovacuum I/O activity

Improve logging of autovacuum I/O activity

This adds some I/O stats to the logging of autovacuum (when the
operation takes long enough that log_autovacuum_min_duration causes it
to be logged), so that it is easier to tune. Notably, it adds buffer
I/O counts (hits, misses, dirtied) and read and write rate.

Authors: Greg Smith and Noah Misch

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9d3b50244357ef4c4e3b6e01f91de599077179c8

Modified Files
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src/backend/commands/vacuum.c | 3 +++
src/backend/commands/vacuumlazy.c | 32 ++++++++++++++++++++++++++++----
src/backend/storage/buffer/bufmgr.c | 20 +++++++++++++++-----
src/backend/utils/init/globals.c | 4 ++++
src/include/miscadmin.h | 4 ++++
5 files changed, 54 insertions(+), 9 deletions(-)