| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Mark Cave-Ayland <m(dot)cave-ayland(at)webbased(dot)co(dot)uk>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Cost of XLogInsert CRC calculations |
| Date: | 2005-03-08 01:50:01 |
| Message-ID: | 1881.1110246601@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Well, we're using the CRC in 3 separate places...
> (1) for xlog records
> (2) for complete blocks copied to xlog
> (3) for control files
> For (1), records are so short that probably CRC16 would be sufficient
> without increasing the error rate noticeably.
> I think I'd like to keep (3) at CRC64...its just too important. Plus
> thats slightly less code to change.
The control files are so short that CRC16 would be plenty.
> My money is on (2) being the source of most of that run-time anyway,
Undoubtedly, so there's not going to be much win from micro-optimization
by having several different CRC functions. I would go for CRC32 across
the board, myself.
regards, tom lane
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