Re: Cost of XLogInsert CRC calculations - Mailing list pgsql-hackers

From Hannu Krosing
Subject Re: Cost of XLogInsert CRC calculations
Date
Msg-id 1116248871.4806.33.camel@fuji.krosing.net
Whole thread Raw
In response to Re: Cost of XLogInsert CRC calculations  ("Mark Cave-Ayland" <m.cave-ayland@webbased.co.uk>)
List pgsql-hackers
On E, 2005-05-16 at 12:12 +0100, Mark Cave-Ayland wrote:
> > -----Original Message-----
> > From: Mark Cave-Ayland [mailto:m.cave-ayland@webbased.co.uk] 
> > Sent: 16 May 2005 09:04
> > To: 'Simon Riggs'
> > Cc: 'Christopher Kings-Lynne'; 'Tom Lane'; 'Bruce Momjian'; 
> > 'pgsql-hackers@postgresql.org'
> > Subject: RE: [HACKERS] Cost of XLogInsert CRC calculations
> 

> 
> Win32 UINT64: 0x782104059a01660 (crc0)             ~158us
> Win32 UINT32: 0x78210405 (crc1), 0x59a01660 (crc0)  ~58us
> FC1 UINT64:   0x782104059a01660 (crc0)              ~76us
> FC1 UINT32:   0x78210405 (crc1), 0x59a01660 (crc0)  ~29us

It would interesting to see how much of the time taken is actual algorithm 
and how much is getting at the data (i.e the fact that the page has to go 
through CPU at all, instead DMA'ing it to disk). 

In your test setup you probably have the whole thing in CPU cache already, 
but still it would be interesting to time the same thing with some simple 
algorithm, like XOR over the whole 8k page, for comparison.

-- 
Hannu Krosing <hannu@skype.net>



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