| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, Abhijit Menon-Sen <ams(at)2ndquadrant(dot)com>, Rahila Syed <rahilasyed(dot)90(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [REVIEW] Re: Compression of full-page-writes |
| Date: | 2014-09-12 20:31:19 |
| Message-ID: | 20140912203119.GC23806@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2014-09-12 22:38:01 +0300, Heikki Linnakangas wrote:
> It's worth noting that there are faster CRC implementations out there than
> what we use. The Slicing-by-4 algorithm was discussed years ago, but was not
> deemed worth it back then IIRC because we typically calculate CRC over very
> small chunks of data, and the benefit of Slicing-by-4 and many other
> algorithms only show up when you work on larger chunks. But a full-page
> image is probably large enough to benefit.
I've recently pondered moving things around so the CRC sum can be
computed over the whole data instead of the individual chain elements. I
think, regardless of the checksum algorithm and implementation we end up
with, that might end up as a noticeable benefit.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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