Re: ShmemAlloc() alignment patch

Martijn van Oosterhout <kleptog@svana.org> writes:
> On Fri, Jul 14, 2006 at 02:50:31PM +0800, Qingqing Zhou wrote:
>> Notice that though newStart is ALIGNOF_BUFFER, ShmemBase is not. Thus the
>> newSpace is not aligned as we disired.

> How can ShmemBase not be aligned? Surely it's page-aligned?

That's certainly what the code expects.  I'm disinclined to apply this
patch unless you can identify a real system where ShmemBase might not
point to a page boundary.

(Note: in a standalone backend, the "shared memory segment" is just a
huge malloc chunk, and so depending on your platform it might not be
page-aligned.  I don't feel a need to add cycles to ShmemAlloc to
optimize this case, though.  We only care about performance in the
normal shared-memory case.)
        regards, tom lane