Re: Make MemoryContextMemAllocated() more precise

On Thu, 2020-03-19 at 11:44 -0400, Robert Haas wrote:
> Procedurally, I think that it is highly inappropriate to submit a
> patch two weeks after the start of the final CommitFest and then
> commit it just over 48 hours later without a single endorsement of
> the
> change from anyone.

Reverted.

Sorry, I misjudged this as a "supporting fix for a specific problem",
but it seems others feel it requires discussion.

> Substantively, I think that whether or not this is improvement
> depends
> considerably on how your OS handles overcommit. I do not have enough
> knowledge to know whether it will be better in general, but would
> welcome opinions from others.

I think omitting the tail of the current block is an unqualified
improvement for the purpose of obeying work_mem, regardless of the OS.
The block sizes keep doubling up to 8MB, and it doesn't make a lot of
sense to count that last large mostly-empty block against work_mem.

Regards,
	Jeff Davis