Re: Increase Vacuum ring buffer.

On Mon, Jul 24, 2017 at 6:37 AM, Sokolov Yura
<funny(dot)falcon(at)postgrespro(dot)ru> wrote:
> Good day, Claudio
>
>
> On 2017-07-22 00:27, Claudio Freire wrote:
>>
>> On Fri, Jul 21, 2017 at 2:41 PM, Sokolov Yura
>> <funny(dot)falcon(at)postgrespro(dot)ru> wrote:
>>>
>>>
>>> My friend noticed, that I didn't said why I bother with autovacuum.
>>> Our customers suffers from table bloating. I've made synthetic
>>> bloating test, and started experiments with modifying micro- and
>>> auto-vacuum. My first attempts were to update FSM early (both in
>>> micro and autovacuum) and update it upto root, not only low level.
>>
>>
>> This FSM thing is probably not a bad idea as well.
>>
>> We're forced to run regular manual vacuums because for some tables
>> autovacuums seems to never be enough, no matter how it's configured,
>> mostly because it gets canceled all the time. These are high-churn,
>> huge tables, so vacuuming them takes hours or days, there's always
>> someone with a conflicting lock at some point that ends up canceling
>> the autovacuum task.
>>
>> The above paragraph triggered me to go check, and it seems in those
>> cases the FSM never gets vacuumed. That's probably not a good thing,
>> but I don't see how to vacuum the FSM after a cancel. So vacuuming the
>> FSM from time to time during long-running vacuums seems like a good
>> idea at this point.
>
>
> Attached patch changes fsm update: instead of updating only lowest
> level, it propagates space increase up to root.
>
> It slows autovacuum a bit, so that I didn't propose it together with
> ring buffer increase.

I was mostly thinking about something like the attached patch.

Simple, unintrusive, and shouldn't cause any noticeable slowdown.