Re: What exactly is our CRC algorithm?

On Thu, Nov 27, 2014 at 11:19:51AM +0530, Abhijit Menon-Sen wrote:
> At 2014-11-26 18:56:52 -0500, bruce@momjian.us wrote:
> >
> > I would test it with fsync=off to remove the fsync delay.  That will
> > simulate an SSD or BBU controller.
> 
> The earlier tests were run with fsync=off.
> 
> I ran another round of the replay tests on the i7 server, this time
> replaying 30GB of WAL segments.
> 
> master
> 
>     16:08:03 16:16:23 08:20
>     16:19:33 16:28:03 08:30
>     16:32:20 16:41:17 08:57
>     16:42:42 16:51:22 08:40
> 
> 8crc
> 
>     16:52:11 16:59:48 07:37
>     17:01:07 17:08:30 07:23
>     17:22:16 17:30:11 07:55
>     17:31:29 17:39:06 07:37
> 
> These are just the results of the last four runs with each branch, but
> the difference was consistent over many more runs.
> 
> To summarise: the slice-by-8 patch (a) increases pure CRC performance by
> a large margin, (b) has a positive effect on reading WAL during replay,
> (c) doesn't hurt XLogInsert in typical cases (which was the main worry).

Thanks, these are good numbers.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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