Re: Add tracking of backend memory allocated to pg_stat_activity

On Wed, Aug 31, 2022 at 12:03:06PM -0400, Reid Thompson wrote:
> Hi Hackers,
> 
> Attached is a patch to 
> Add tracking of backend memory allocated to pg_stat_activity

> +  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',

In the past, there was concern about making pg_stat_activity wider by
adding information that's less-essential than what's been there for
years.  This is only an int64, so it's not "wide", but I wonder if
there's another way to expose this information?  Like adding backends to
pg_get_backend_memory_contexts() , maybe with another view on top of
that ?

+                * shown allocated in pgstat_activity when the creator destroys the
                                                                                                          
 

pg_stat

> +         * Posix creation calls dsm_impl_posix_resize implying that resizing
> +         * occurs or may be added in the future. As implemented
> +         * dsm_impl_posix_resize utilizes fallocate or truncate, passing the
> +         * whole new size as input, growing the allocation as needed * (only
> +         * truncate supports shrinking). We update by replacing the * old

wrapping caused extraneous stars

> +     * Do not allow backend_mem_allocated to go below zero. ereport if we
> +     * would have. There's no need for a lock around the read here asit's

as it's

> +        ereport(LOG, (errmsg("decrease reduces reported backend memory allocated below zero; setting reported to
0")));

errmsg() doesn't require the outside paranthesis since a couple years
ago.

> +    /*
> +     * Until header allocation is included in context->mem_allocated cast to
> +     * slab and decrement the headerSize

add a comma before "cast" ?

-- 
Justin