Re: Misaligned BufferDescriptors causing major performance problems on AMD

On 2014-02-05 12:36:42 -0500, Robert Haas wrote:
> >> It may well be that your proposal is spot on. But I'd like to see some
> >> data-structure-by-data-structure measurements, rather than assuming that
> >> alignment must be a good thing.
> >
> > I am fine with just aligning BufferDescriptors properly. That has
> > clearly shown massive improvements.
>
> I thought your previous idea of increasing BUFFERALIGN to 64 bytes had
> a lot to recommend it.

Good.

I wonder if we shouldn't move that bit of logic:
if (size >= BUFSIZ)
newStart = BUFFERALIGN(newStart);
out of ShmemAlloc() and instead have a ShmemAllocAligned() and
ShmemInitStructAligned() that does it. So we can sensibly can control it
per struct.

> But that doesn't mean it doesn't need testing.

I feel the need here, to say that I never said it doesn't need testing
and never thought it didn't...

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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