Horton
Menu

Re: Enabling Checksums

Jeff Davis <pgsql@j-davis.com>

View thread
From: Jeff Davis <pgsql@j-davis.com>
To: Ants Aasma <ants@cybertec.at>
Cc: Robert Haas <robertmhaas@gmail.com>, Greg Smith <greg@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Florian Pflug <fgp@phlo.org>, Andres Freund <andres@2ndquadrant.com>, Bruce Momjian <bruce@momjian.us>, Heikki Linnakangas <hlinnakangas@vmware.com>, Simon Riggs <simon@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2013-04-22T19:22:21Z
Lists: pgsql-hackers 
On Mon, 2013-04-22 at 19:25 +0300, Ants Aasma wrote:
> I was just now writing up a generic C based patch based on the
> parallel FNV-1a + shift that we discussed with Florian with an added
> round of mixing. Testing the performance in isolation indicates that:
> 1) it is about an order of magnitude faster than the Sarwate CRC
> method used in Postgresql.
> 2) it is about 2x faster than fastest software based CRC method.
> 3) by using -msse4.1 -funroll-loops -ftree-vectorize compilation
> options the performance improves 5x. (within 20% of handcoded ASM)

That's great news!

This means that we can have a simple C implementation in a separate
file, and pass a few build flags when compiling just that file (so it
doesn't affect other code). That should make reviewers/committers happy
(including me).

FWIW, that was my last real concern about FNV (reviewability). I'm not
worried about the performance based on your analysis; nor am I worried
about the error detection rate.

Regards,
	Jeff Davis