Re: SLRU statistics

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.fujii@oss.nttdata.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
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