Re: [REVIEW] Re: Compression of full-page-writes

That's not entirely true. CRC-32C beats pretty much everything with the
same length quality-wise and has both hardware implementations and highly
optimized software versions.
Em 12/09/2014 17:18, "Ants Aasma" <ants(at)cybertec(dot)at> escreveu:

> On Fri, Sep 12, 2014 at 10:38 PM, Heikki Linnakangas
> <hlinnakangas(at)vmware(dot)com> wrote:
> > I don't mean that we should abandon this patch - compression makes the
> WAL
> > smaller which has all kinds of other benefits, even if it makes the raw
> TPS
> > throughput of the system worse. But I'm just saying that these TPS
> > comparisons should be taken with a grain of salt. We probably should
> > consider switching to a faster CRC algorithm again, regardless of what
> we do
> > with compression.
>
> CRC is a pretty awfully slow algorithm for checksums. We should
> consider switching it out for something more modern. CityHash,
> MurmurHash3 and xxhash look like pretty good candidates, being around
> an order of magnitude faster than CRC. I'm hoping to investigate
> substituting the WAL checksum algorithm 9.5.
>
> Given the room for improvement in this area I think it would make
> sense to just short-circuit the CRC calculations for testing this
> patch to see if the performance improvement is due to less data being
> checksummed.
>
> Regards,
> Ants Aasma
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