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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Cc: Shinoda, Noriyoshi (PN Japan A&PS Delivery) <noriyoshi.shinoda@hpe.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>
Cc: tsunakawa.takay@fujitsu.com <tsunakawa.takay@fujitsu.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: SLRU statistics
Date: Tue, 7 Apr 2020 19:29:06 +0200
Message-ID: <20200407172906.lqbipjyhxokudibx@development> (raw)
In-Reply-To: <CAGz5QCKMf7BgT-oR4yTFYuDBLu55rOG82-Mk=P1-4BaMpnLkZA@mail.gmail.com>
References: <20200229122441.ow7gnnqgesmojyc3@development>
	<20200229144426.GA32500@alvherre.pgsql>
	<20200229205518.xrxo535zgd7cl6no@development>
	<20200327004111.md4suoi6u5suv2qe@development>
	<20200328002630.2nz5y3dvymqnvxtv@development>
	<20200402004136.wodwftan45mcwggm@development>
	<DF4PR8401MB11472F9C76B91994198FF7D3EEC60@DF4PR8401MB1147.NAMPRD84.PROD.OUTLOOK.COM>
	<20200402122933.pioe6336vrdzrgrb@development>
	<CAGz5QCKMf7BgT-oR4yTFYuDBLu55rOG82-Mk=P1-4BaMpnLkZA@mail.gmail.com>

On Tue, Apr 07, 2020 at 05:01:37PM +0530, Kuntal Ghosh wrote:
>Hello Tomas,
>
>On Thu, Apr 2, 2020 at 5:59 PM Tomas Vondra
><tomas.vondra@2ndquadrant.com> wrote:
>> Thank you for the patch, pushed.
>>
>In SimpleLruReadPage_ReadOnly, we first try to find the SLRU page in
>shared buffer under shared lock, then conditionally visit
>SimpleLruReadPage if reading is necessary. IMHO, we should update
>hit_count if we can find the buffer in SimpleLruReadPage_ReadOnly
>directly. Am I missing something?
>
>Attached a patch for the same.
>

Yes, I think that's correct - without this we fail to account for
(possibly) a quite significant number of hits. Thanks for the report,
I'll get this pushed later today.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services 





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