Re: Limiting memory allocation

Greetings,

* Jan Wieck (jan(at)wi3ck(dot)info) wrote:
> On 5/17/22 18:30, Stephen Frost wrote:
> >This isn’t actually a solution though and that’s the problem- you end up
> >using swap but if you use more than “expected” the OOM killer comes in and
> >happily blows you up anyway. Cgroups are containers and exactly what kube
> >is doing.
>
> Maybe I'm missing something, but what is it that you would actually consider
> a solution? Knowing your current memory consumption doesn't make the need
> for allocating some right now go away. What do you envision the response of
> PostgreSQL to be if we had that information about resource pressure? I don't
> see us using mallopt(3) or malloc_trim(3) anywhere in the code, so I don't
> think any of our processes give back unused heap at this point (please
> correct me if I'm wrong). This means that even if we knew about the memory
> pressure of the system, adjusting things like work_mem on the fly may not do
> much at all, unless there is a constant turnover of backends.
>
> So what do you propose PostgreSQL's response to high memory pressure to be?

Fail the allocation, just how most PG systems are set up to do. In such
a case, PG will almost always be able to fail the transaction, free up
the memory used, and continue running *without* ending up with a crash.

Thanks,

Stephen