| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 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: | 2020-05-13 15:28:46 |
| Message-ID: | 20200513152846.goee2c5xrly52ga2@development |
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| Lists: | pgsql-hackers |
On Wed, May 13, 2020 at 11:46:30PM +0900, Fujii Masao wrote:
>
>
>On 2020/05/13 23:26, Tom Lane wrote:
>>Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> writes:
>>>On 2020/05/13 17:21, Tomas Vondra wrote:
>>>>On Wed, May 13, 2020 at 04:10:30PM +0900, Fujii Masao wrote:
>>>>>Also I found another minor issue; SLRUStats has not been initialized to 0
>>>>>and which could update the counters unexpectedly. Attached patch fixes
>>>>>this issue.
>>
>>>Pushed both. Thanks!
>>
>>Why is that necessary? A static variable is defined by C to start off
>>as zeroes.
>
>Because SLRUStats is not a static variable. No?
>
I think it counts as a variable with "static storage duration" per 6.7.8
(para 10), see [1]. I wasn't aware of this either, but it probably means
the memset is unnecessary.
Also, it seems a bit strange/confusing to handle this differently from
BgWriterStats. And that worked fine without the init for years ...
[1] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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