Re: pg_shmem_allocations view

Robert Haas <robertmhaas@gmail.com> writes:
> On Sun, May 4, 2014 at 7:50 AM, Andres Freund <andres@2ndquadrant.com> wrote:
>> Thinking about this, I think it was a mistake to not add a 'name' field
>> to dynamic shared memory's dsm_control_item.

> Well, right now a dsm_control_item is 8 bytes.  If we add a name field
> of our usual 64 bytes, they'll each be 9 times bigger.

And the controlled shared segment is likely to be how big exactly?  It's
probably not even possible for it to be smaller than a page size, 4K or
so depending on the OS.  I agree with Andres that a name would be a good
idea; complaining about the space needed to hold it is penny-wise and
pound-foolish.

> I'm quite in favor of having something like this for the main shared
> memory segment, but I think that's 9.5 material at this point.

If you're prepared to break the current APIs later to add a name parameter
(which would have to be required, if it's to be useful at all), then sure,
put the question off till 9.5.
        regards, tom lane