| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Ants Aasma <ants(dot)aasma(at)eesti(dot)ee> |
| Cc: | Andreas Karlsson <andreas(at)proxel(dot)se>, Stephen Frost <sfrost(at)snowman(dot)net>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Checksums by default? |
| Date: | 2017-02-24 20:30:29 |
| Message-ID: | 20170224203029.GH23209@momjian.us |
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| Lists: | pgsql-hackers |
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(at)momjian(dot)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(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
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