Re: [HACKERS] Should we cacheline align PGXACT?

On Tue, Feb 14, 2017 at 3:57 PM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:

Alexander Korotkov wrote:
> On Mon, Feb 13, 2017 at 7:07 PM, Alvaro Herrera <alvherre@2ndquadrant.com>
> wrote:

> > Re the coding of the padding computation, seems it'd be better to use
> > our standard "offsetof(last-struct-member) + sizeof(last-struct-member)"
> > rather than adding each of the members' sizes individually.
>
> It was done so in order to evade extra level of nesting for PGXACT.  See
> discussion with Tom Lane in [1] and upthread.

Yes, I understand.  I just mean that it could be done something like
this:

#define PGXACTPadSize (PG_CACHE_LINE_SIZE - (offsetof(PGXACT, nxid) + sizeof(uint8)))

Yes, but I can't use such macro in the definition of PGXACT itself.