> -----Original Message----- > From: Tom Lane [mailto:[EMAIL PROTECTED] > Sent: 27 May 2005 15:00 > To: Mark Cave-Ayland (External) > Cc: 'Manfred Koizar'; 'Greg Stark'; 'Bruce Momjian'; > pgsql-hackers@postgresql.org > Subject: Re: [HACKERS] Cost of XLogInsert CRC calculations
(cut) > Not sure I believe these numbers. Shouldn't 2x32 be about twice as > slow as just one 32-bit CRC? Also I've just quickly tested on the Xeon Linux FC1 box I used with my original program using Manfred's program and the margin is even closer: Opt 32 32a 32b 2x32 64 64a 64b ------------------------------------------------------ O1 2.75 2.81 2.71 3.16 3.53 3.64 7.25 O2 2.75 2.78 2.87 2.94 7.63 10.61 11.93 O3 2.84 2.85 3.03 2.99 7.63 7.64 7.71 I don't know whether gcc is just producing an inefficient CRC32 compared to 2x32 but the results seem very odd.... There must be something else we are missing? Kind regards, Mark. ------------------------ WebBased Ltd South West Technology Centre Tamar Science Park Plymouth PL6 8BT T: +44 (0)1752 797131 F: +44 (0)1752 791023 W: http://www.webbased.co.uk ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
