Re: Synchronized Scan benchmark results

Jeff,

Your conclusions sound great - can you perhaps put the timings in a column
in your table so we can confirm them?

- Luke

On 4/2/07 4:14 PM, "Jeff Davis" <pgsql(at)j-davis(dot)com> wrote:

> I posted some fairly detailed benchmark results for my Synchronized Scan
> patch and it's interactions with Simon Riggs' Recycle Buffers patch
> here:
>
> http://j-davis.com/postgresql/patch15-results.html
>
> The results are in the form of log files that contain lots of useful
> debugging info:
>
> * log_executor_stats is on (meaning it shows cache hit rate)
> * the pid, timestamp, and pagenumber being retrieved (for every 5k pages
> read)
> * the duration of each scan
>
> The results are very positive and quite conclusive.
>
> However, the "sync_seqscan_offset" aspect of my patch, which attempts to
> use pages that were cached before the scan began, did not show a lot of
> promise. That aspect of my patch may end up being cut.
>
> The primary aspect of my patch, the Synchronized Scanning, performed
> great though. Even the CFQ scheduler, that does not appear to properly
> read ahead, performed substantially better than plain 8.2.3. And even
> better, Simon's patch didn't seem to hurt Synchronized Scans at all.
>
> Out of the 36 runs I did, a couple appear anomalous. I will retest those
> soon.
>
> Note: I posted the versions of the patches that I used for the tests on
> the page above. The version of Simon's patch that I used did not apply
> cleanly to 8.2.3, but the only problem appeared to be in copy.c, so I
> went ahead with the tests. If this somehow compromised the patch, then
> let me know.
>
> Regards,
> Jeff Davis
>
>
>
>
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