Re: When do vacuumed pages/tuples become available for reuse?

>
> vacuum frees tuples just fine. It's just that by the time each run
> finishes many more accumulate due to table update activity, ad nauseum. So
> this unused space constantly grows. Here's a sample autovacuum run:
>
> 2019-04-11 19:39:44.450841500 [] LOG: automatic vacuum of table
> "foo.public.bar": index scans: 1
> 2019-04-11 19:39:44.450843500 pages: 0 removed, 472095 remain, 4 skipped
> due to pins, 39075 skipped frozen
> 2019-04-11 19:39:44.450844500 tuples: 19150 removed, 2725811 remain, 465
> are dead but not yet removable
> 2019-04-11 19:39:44.450845500 buffer usage: 62407557 hits, 6984769
> misses, 116409 dirtied
> 2019-04-11 19:39:44.450846500 avg read rate: 16.263 MB/s, avg write
> rate: 0.271 MB/s
> 2019-04-11 19:39:44.450847500 system usage: CPU 59.05s/115.26u sec
> elapsed 3355.28 sec
>

Maybe I am off base, but those read/write rates seem very low. Is this
running on spinny disks? Also, less than half a million rows remain and 2.7
million dead but not removed in this auto vacuum. It seems to indicate that
auto vacuum is not as aggressive as it needs to be. Have you verified that
it blocks normal activity when autovacuum does more work each pass? If you
are hardware bound, could you use partitioning to allow auto vacuum to work
on the partitions separately and perhaps keep up?