Re: pglz performance

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Vladimir Leskov <vladimirlesk(at)yandex-team(dot)ru>
Subject: Re: pglz performance
Date: 2019-05-17 01:44:24
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On Thu, May 16, 2019 at 10:13:22PM +0500, Andrey Borodin wrote:
> Meanwhile I made some enhancements to test suit:
> Intel Server
> NOTICE: 00000: Decompressor pglz_decompress_hacked result 10.346763
> NOTICE: 00000: Decompressor pglz_decompress_hacked8 result 11.192078
> NOTICE: 00000: Decompressor pglz_decompress_hacked16 result 11.957727
> NOTICE: 00000: Decompressor pglz_decompress_vanilla result 14.262256
> ARM Server
> NOTICE: Decompressor pglz_decompress_hacked result 12.966668
> NOTICE: Decompressor pglz_decompress_hacked8 result 13.004935
> NOTICE: Decompressor pglz_decompress_hacked16 result 13.043015
> NOTICE: Decompressor pglz_decompress_vanilla result 18.239242
> Power9 Server
> NOTICE: Decompressor pglz_decompress_hacked result 10.992974
> NOTICE: Decompressor pglz_decompress_hacked8 result 11.747443
> NOTICE: Decompressor pglz_decompress_hacked16 result 11.026342
> NOTICE: Decompressor pglz_decompress_vanilla result 16.375315
> Intel laptop
> NOTICE: Decompressor pglz_decompress_hacked result 9.445808
> NOTICE: Decompressor pglz_decompress_hacked8 result 9.105360
> NOTICE: Decompressor pglz_decompress_hacked16 result 9.621833
> NOTICE: Decompressor pglz_decompress_vanilla result 10.661968
> From these results pglz_decompress_hacked looks best.

That's nice.

From the numbers you are presenting here, all of them are much better
than the original, and there is not much difference between any of the
patched versions. Having a 20%~30% improvement with a patch is very

After that comes the simplicity and the future maintainability of what
is proposed. I am not much into accepting a patch which has a 1%~2%
impact for some hardwares and makes pglz much more complex and harder
to understand. But I am really eager to see a patch with at least a
10% improvement which remains simple, even more if it simplifies the
logic used in pglz.

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