Re: SLRU statistics

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>
Cc: "Shinoda, Noriyoshi (PN Japan A&PS Delivery)" <noriyoshi(dot)shinoda(at)hpe(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>, "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: SLRU statistics
Date: 2020-04-07 17:29:06
Message-ID: 20200407172906.lqbipjyhxokudibx@development
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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(dot)vondra(at)2ndquadrant(dot)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.


Tomas Vondra
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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