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In-Reply-To: <bee20393-b1be-40ff-9619-334762e64713@iki.fi>
From: Maxim Orlov <orlovmg@gmail.com>
Date: Thu, 20 Nov 2025 19:30:51 +0300
Message-ID: 
 <CACG=ezbDgXvgNcxMmiCNZR1g95CBT+Y2rVhZWa_1SuOWeFREDw@mail.gmail.com>
Subject: Re: POC: make mxidoff 64 bits
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: wenhui qiu <qiuwenhuifx@gmail.com>,
 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
 Alexander Korotkov <aekorotkov@gmail.com>,
	Postgres hackers <pgsql-hackers@lists.postgresql.org>
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On Wed, 19 Nov 2025 at 19:20, Heikki Linnakangas <hlinnaka@iki.fi> wrote:

>
> I think those recipes need to be adjusted for 64-bit offsets.

Yes, we need to do it.

Sorry if this is too obvious, but with 32-bit offsets, we get:
SLRU_PAGES_PER_SEGMENT * BLKSZ / sizeof(MXOff) =
    32 * 8192 / 4 = 65,536 mxoff per segment.

Now, with 64-bits offsets, we should have half as much.

-- 
Best regards,
Maxim Orlov.

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<div dir=3D"ltr"><div dir=3D"ltr"></div><br><div class=3D"gmail_quote gmail=
_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, 19 Nov 2025=
 at 19:20, Heikki Linnakangas &lt;<a href=3D"mailto:hlinnaka@iki.fi">hlinna=
ka@iki.fi</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=
=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding=
-left:1ex">
<br>
I think those recipes need to be adjusted for 64-bit offsets.</blockquote><=
/div>Yes, we need to do it.<br><br><span class=3D"gmail-HwtZe" lang=3D"en">=
<span class=3D"gmail-jCAhz gmail-ChMk0b"><span class=3D"gmail-ryNqvb">Sorry=
 if this is too obvious, but w</span></span></span>ith 32-bit offsets, we g=
et:<br><div>SLRU_PAGES_PER_SEGMENT * BLKSZ / sizeof(MXOff) =3D</div><div>=
=C2=A0 =C2=A0 32 * 8192 / 4 =3D=C2=A065,536 mxoff per segment.</div>=C2=A0 =
=C2=A0 <br><div>Now, with 64-bits offsets, we should have half as much.</di=
v><div><br></div><span class=3D"gmail_signature_prefix">-- </span><br><div =
dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><div>Best regards,<b=
r></div><div>Maxim Orlov.</div></div></div></div>

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