Horton

Re: Inlining comparators as a performance optimisation

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Peter Geoghegan <peter@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, PG Hackers <pgsql-hackers@postgresql.org>
Date: 2011-11-21T22:55:18Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Speed up conversion of signed integers to C strings.

  2. Remove some unnecessary tests of pgstat_track_counts.

  3. Remove cvs keywords from all files.

  4. Code cleanup for function prototypes: change two K&R-style prototypes

  5. Use Min() instead of min() in qsort, for consistency and to avoid

  6. pgindent run for 8.2.

  7. Switch over to using our own qsort() all the time, as has been proposed

On Tue, Sep 20, 2011 at 7:53 PM, Peter Geoghegan <peter@2ndquadrant.com> wrote:
> I don't think that the fact that that happens is at all significant at
> this early stage, and it never even occurred to me that you'd think
> that it might be. I was simply disclosing a quirk of this POC patch.
> The workaround is probably to use a macro instead. For the benefit of
> those that didn't follow the other threads, the macro-based qsort
> implementation, which I found to perform significantly better than
> regular qsort(), runs like this on my laptop when I built at 02 with
> GCC 4.6 just now:
>
> C stdlib quick-sort time elapsed: 2.092451 seconds
> Inline quick-sort time elapsed: 1.587651 seconds

Results on my machine, for what they're worth:

[rhaas inline_compar_test]$ gcc -O0 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 2.366762 seconds
Inline quick-sort time elapsed: 1.807951 seconds
[rhaas inline_compar_test]$ gcc -O1 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 1.970473 seconds
Inline quick-sort time elapsed: 1.002765 seconds
[rhaas inline_compar_test]$ gcc -O2 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 1.966408 seconds
Inline quick-sort time elapsed: 0.958999 seconds
[rhaas inline_compar_test]$ gcc -O3 qsort-inline-benchmark.c
[rhaas inline_compar_test]$ ./a.out
C stdlib quick-sort time elapsed: 1.988693 seconds
Inline quick-sort time elapsed: 0.975090 seconds

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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