Date: Fri, 1 Nov 2019 17:59:50 +0100
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	Andrey Borodin <x4mmm@yandex-team.ru>, Gasper Zejn <zejn@owca.info>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: pglz performance
Message-ID: <20191101165950.b5azncggaqfan5fi@development>
References: <3c2d92d0-e715-f9ed-e1a7-3c510ed65940@2ndquadrant.com>
 <20191101154828.GA15829@alvherre.pgsql>
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On Fri, Nov 01, 2019 at 12:48:28PM -0300, Alvaro Herrera wrote:
>On 2019-Nov-01, Peter Eisentraut wrote:
>
>> On 2019-10-25 07:05, Andrey Borodin wrote:
>> > > 21 окт. 2019 г., в 14:09, Andrey Borodin <x4mmm@yandex-team.ru> написал(а):
>> > >
>> > > With Silesian corpus pglz_decompress_hacked is actually decreasing performance on high-entropy data.
>> > > Meanwhile pglz_decompress_hacked8 is still faster than usual pglz_decompress.
>> > > In spite of this benchmarks, I think that pglz_decompress_hacked8 is safer option.
>> >
>> > Here's v3 which takes into account recent benchmarks with Silesian Corpus and have better comments.
>>
>> Your message from 21 October appears to say that this change makes the
>> performance worse.  So I don't know how to proceed with this.
>
>As I understand that report, in these results "less is better", so the
>hacked8 variant shows better performance (33.8) than current (42.5).
>The "hacked" variant shows worse performance (48.2) that the current
>code.  The "in spite" phrase seems to have been a mistake.
>
>I am surprised that there is so much variability in the performance
>numbers, though, based on such small tweaks of the code.
>

I'd try running the benchmarks to verify the numbers, and maybe do some
additional tests, but it's not clear to me which patches should I use.

I think the last patches with 'hacked' and 'hacked8' in the name are a
couple of months old, and the recent posts attach just a single patch.
Andrey, can you post current versions of both patches?


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services