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From: Nathan Bossart <[email protected]>
To: David G. Johnston <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Odd off-by-one dirty buffers and checkpoint buffers written
Date: Tue, 19 Apr 2022 16:36:51 -0700
Message-ID: <20220419233651.GA2578385@nathanxps13> (raw)
In-Reply-To: <CAKFQuwab2tVr64Zw2stb5wJRMds_oZBzKuosKLHR6g56vMANOg@mail.gmail.com>
References: <CAKFQuwab2tVr64Zw2stb5wJRMds_oZBzKuosKLHR6g56vMANOg@mail.gmail.com>

On Tue, Apr 19, 2022 at 04:21:21PM -0700, David G. Johnston wrote:
> I've done this four times in a row and while the number of dirty buffers
> shown each time vary (see below) I see that "wrote N buffers" is always
> exactly one more than the total count of dirty buffers.  I'm just curious
> if anyone has a quick answer for this unusual correspondence.

I see that SlruInternalWritePage() increments ckpt_bufs_written, so my
first guess would be that it's due to something like CheckPointCLOG().

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com






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