On Thu, 10 Aug 2023 at 20:33, Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
> My point is what's relevant here is how much net memory planner asked
> for.
But that's not what your patch is reporting. All you're reporting is
the difference in memory that's *currently* palloc'd from before and
after the planner ran. If we palloc'd 600 exabytes then pfree'd it
again, your metric won't change.
I'm struggling a bit to understand your goals here. If your goal is
to make a series of changes that reduces the amount of memory that's
palloc'd at the end of planning, then your patch seems to suit that
goal, but per the quote above, it seems you care about how many bytes
are palloc'd during planning and your patch does not seem track that.
With your patch as it is, to improve the metric you're reporting we
could go off and do things like pfree Paths once createplan.c is done,
but really, why would we do that? Just to make the "Planning Memory"
metric looks better doesn't seem like a worthy goal.
Instead, if we reported the context's mem_allocated, then it would
give us the flexibility to make changes to the memory context code to
have the metric look better. It might also alert us to planner
inefficiencies and problems with new code that may cause a large spike
in the amount of memory that gets allocated. Now, I'm not saying we
should add a patch that shows mem_allocated. I'm just questioning if
your proposed patch meets the goals you're trying to achieve. I just
suggested that you might want to consider something else as a metric
for your memory usage reduction work.
David