Re: Add tracking of backend memory allocated to pg_stat_activity

Hi,

On Fri, Sep 09, 2022 at 12:34:15PM -0400, Stephen Frost wrote:

While we are at it, what do you think about also recording the max memory
allocated by a backend? (could be useful and would avoid sampling for which
there is no guarantee to sample the max anyway).

What would you do with that information..?  By itself, it doesn't strike
me as useful.  Perhaps it'd be interesting to grab the max required for
a particular query in pg_stat_statements or such but again, that's a
very different thing.

Storing the maxrss per backend somewhere would be useful (and avoid the
issue of "sampling" with top), after I agree that it ought to be exposed
to a view.  For example, it might help to determine whether (and which!)
backends are using large multiple of work_mem, and then whether that can
be increased.  If/when we had a "memory budget allocator", this would
help to determine how to set its GUCs, maybe to see "which backends are
using the work_mem that are precluding this other backend from using
efficient query plan".

+1.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com