Re: WIP: WAL prefetch (another approach)

From: Andres Freund <andres(at)anarazel(dot)de>
To: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Stephen Frost <sfrost(at)snowman(dot)net>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Jakub Wartak <Jakub(dot)Wartak(at)tomtom(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: WAL prefetch (another approach)
Date: 2021-04-28 16:32:45
Message-ID: 20210428163245.ff67pb2ii5irr5zr@alap3.anarazel.de
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Hi,

On 2021-04-22 13:59:58 +1200, Thomas Munro wrote:
> On Thu, Apr 22, 2021 at 1:21 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > I've also tried to reproduce on 32-bit and 64-bit Intel, without
> > success. So if this is real, maybe it's related to being big-endian
> > hardware? But it's also quite sensitive to $dunno-what, maybe the
> > history of WAL records that have already been replayed.
>
> Ah, that's interesting. There are a couple of sparc64 failures and a
> ppc64 failure in the build farm, but I couldn't immediately spot what
> was wrong with them or whether it might be related to this stuff.
>
> Thanks for the clues. I'll see what unusual systems I can find to try
> this on....

FWIW, I've run 32 and 64 bit x86 through several hundred regression
cycles, without hitting an issue. For a lot of them I set
checkpoint_timeout to a lower value as I thought that might make it more
likely to reproduce an issue.

Tom, any chance you could check if your machine repros the issue before
these commits?

Greetings,

Andres Freund

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