Re: SLRU statistics

On Tue, Jan 21, 2020 at 05:09:33PM +0900, Masahiko Sawada wrote:
>On Tue, 21 Jan 2020 at 01:38, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>>
>> On Mon, Jan 20, 2020 at 01:04:33AM +0000, tsunakawa(dot)takay(at)fujitsu(dot)com wrote:
>> >From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
>> >> One of the stats I occasionally wanted to know are stats for the SLRU
>> >> stats (we have couple of those - clog, subtrans, ...). So here is a WIP
>> >> version of a patch adding that.
>
>+1
>
>> >
>> >How can users take advantage of this information? I think we also need
>> >the ability to set the size of SLRU buffers. (I want to be freed from
>> >the concern about the buffer shortage by setting the buffer size to its
>> >maximum. For example, CLOG would be only 1 GB.)
>> >
>>
>> You're right the users can't really take advantage of this - my primary
>> motivation was providing a feedback for devs, benchmarking etc. That
>> might have been done with DEBUG messages or something, but this seems
>> more convenient.
>
>I've not tested the performance impact but perhaps we might want to
>disable these counter by default and controlled by a GUC. And similar
>to buffer statistics it might be better to inline
>pgstat_count_slru_page_xxx function for better performance.
>

Hmmm, yeah. Inlining seems like a good idea, and maybe we should have
something like track_slru GUC.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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