Re: Pinning a buffer in TupleTableSlot is unnecessary

On Mon, Nov 14, 2016 at 10:17 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> I think so, yes. IIRC I discussed it with Noah and Peter G. at a
> conference recently. We'd basically mark the content of shared buffers
> inaccessible at backend startup, and mark it accessible whenever a
> PinBuffer() happens, and then inaccessible during unpinning. We probably
> have to exclude the page header though, as we intentionally access them
> unpinned in some cases IIRC.

BTW, I recently noticed that the latest version of Valgrind, 3.12,
added this new feature:

* Memcheck:

- Added meta mempool support for describing a custom allocator which:
- Auto-frees all chunks assuming that destroying a pool destroys all
objects in the pool
- Uses itself to allocate other memory blocks

It occurred to me that we might be able to make good use of this. To
be clear, I don't think that there is reason to tie it to adding the
PinBuffer() stuff, which we've been talking about for years now. It
just caught my eye.

--
Peter Geoghegan