> -----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 > > > "Mark Cave-Ayland" <[EMAIL PROTECTED]> writes: > > Opt 32 32a 32b 2x32 64 64a 64b > > -------------------------------------------------------- > > O1 4.91 4.86 5.43 6.00 11.4 11.39 11.39 > > O2 4.96 4.94 4.69 5.18 15.86 18.75 24.73 > > O3 4.82 4.83 4.64 5.18 15.14 13.77 14.73 > > Not sure I believe these numbers. Shouldn't 2x32 be about > twice as slow as just one 32-bit CRC?
Well it surprised me, although Manfred's results with VC6 on /MaxSpeed show a similar margin. The real killer has to be that I wrote a CRC32 routine in x86 inline assembler (which in comparison to the gcc-produced version stores the CRC for each iteration in registers instead of in memory as part of the current frame) which comes in at 6.5s.... 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 4: Don't 'kill -9' the postmaster
