Horton

Re: Inlining comparators as a performance optimisation

Simon Riggs <simon@2ndquadrant.com>

View thread
From: Simon Riggs <simon@2ndQuadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Peter Geoghegan <peter@2ndquadrant.com>, PG Hackers <pgsql-hackers@postgresql.org>
Date: 2011-09-21T06:55:55Z
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 3:51 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

>> This performance patch differs from most in that it's difficult in
>> principle to imagine a performance regression occurring.
>
> Really?  N copies of the same code could lead to performance loss just
> due to code bloat (ie, less of a query's inner loops fitting in CPU
> cache).  Not to mention the clear regression in maintainability.  So
> I'm disinclined to consider this sort of change without a significantly
> bigger win than you're suggesting above (no, I don't even consider the
> -O0 number attractive, let alone what you're finding at -O2).

More copies of the code are somewhat annoying, but its only 100 lines
of code in one module and we can easily have specific tests for each.
The extra code size is minor in comparison to the reams of code we add
elsewhere.

It's a surprisingly good win for such a common use case. Well done, Peter.

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services