From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
cc: Thomas Munro <thomas.munro@gmail.com>, Andres Freund <andres@anarazel.de>,
        Stephen Frost <sfrost@snowman.net>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        David Steele <david@pgmasters.net>,
        Dmitry Dolgov <9erthalion6@gmail.com>,
        Jakub Wartak <Jakub.Wartak@tomtom.com>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: WIP: WAL prefetch (another approach)
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Comments: In-reply-to Tomas Vondra <tomas.vondra@enterprisedb.com>
	message dated "Tue, 04 May 2021 14:37:22 +0200"
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Date: Tue, 04 May 2021 09:46:12 -0400
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Tomas Vondra <tomas.vondra@enterprisedb.com> writes:
> On 5/3/21 7:42 AM, Thomas Munro wrote:
>> Hmm, yeah that does seem plausible.  It would be nice to see a report
>> from any other system though.  I'm still trying, and reviewing...

> FWIW I've ran the test (make installcheck-parallel in a loop) on four 
> different machines - two x86_64 ones, and two rpi4. The x86 boxes did 
> ~1000 rounds each (and one of them had 5 local replicas) without any 
> issue. The rpi4 machines did ~50 rounds each, also without failures.

Yeah, I have also spent a fair amount of time trying to reproduce it
elsewhere, without success so far.  Notably, I've been trying on a
PPC Mac laptop that has a fairly similar CPU to what's in the G4,
though a far slower disk drive.  So that seems to exclude theories
based on it being PPC-specific.

I suppose that if we're unable to reproduce it on at least one other box,
we have to write it off as hardware flakiness.  I'm not entirely
comfortable with that answer, but I won't push for reversion of the WAL
patches without more evidence that there's a real issue.

			regards, tom lane