On Fri, Feb 24, 2017 at 10:09:50PM +0200, Ants Aasma wrote:
> On Fri, Feb 24, 2017 at 9:37 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > Oh, that's why we will hopefully eventually change the page checksum
> > algorithm to use the special CRC32 instruction, and set a new checksum
> > version --- got it. I assume there is currently no compile-time way to
> > do this.
>
> Using CRC32 as implemented now for the WAL would be significantly
> slower than what we have now due to instruction latency. Even the best
> theoretical implementation using the CRC32 instruction would still be
> about the same speed than what we have now. I haven't seen anybody
> working on swapping out the current algorithm. And I don't really see
> a reason to, it would introduce a load of headaches for no real gain.
Uh, I am confused. I thought you said we were leaving some performance
on the table. What is that? I though CRC32 was SSE4.1. Why is CRC32
good for the WAL but bad for the page checksums? What about the WAL
page images?
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
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