Re: Parallel Seq Scan vs kernel read ahead

From: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
To: Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Parallel Seq Scan vs kernel read ahead
Date: 2020-05-20 21:48:42
Message-ID: CA+hUKG+qe-kVP2ticZ_CZF+JH38Bh3oKZV_MZ4u4yBJTPFMJdQ@mail.gmail.com
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On Wed, May 20, 2020 at 11:03 PM Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> wrote:
> Time: 47767,916 ms (00:47,768)
> Time: 32645,448 ms (00:32,645)

Just to make sure kernel caching isn't helping here, maybe try making
the table 2x or 4x bigger? My test was on a virtual machine with only
4GB RAM, so the table couldn't be entirely cached.

> How display " -> execution time 5.2s, average read size ="?

Execution time is what you showed, and average read size should be
inside the Windows performance window somewhere (not sure what it's
called).

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