On 2016-03-28 11:48:46 +0530, Dilip Kumar wrote:
> On Sun, Mar 27, 2016 at 5:48 PM, Andres Freund <andres@anarazel.de> wrote:
>
> >
> > What's sizeof(BufferDesc) after applying these patches? It should better
> > be <= 64...
> >
>
> It is 72.
Ah yes, miscalculated the required alignment. Hm. So we got to get this
smaller. I see three approaches:
1) Reduce the spinlock size on ppc. That actually might just work by replacing "unsigned int" by "unsigned char"
2) Replace the lwlock spinlock by a bit in LWLock->state. That'd avoid embedding the spinlock, and actually might
allowto avoid one atomic op in a number of cases.
3) Shrink the size of BufferDesc by removing buf_id; that'd bring it to 64byte.
I'm a bit hesitant to go for 3), because it'd likely end up adding a bit
of arithmetic to a number of places in bufmgr.c. Robert, what do you
think?
Andres