Re: What does "[backends] should seldom or never need to wait for a write to occur" mean?

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От Chris Wilson
Тема Re: What does "[backends] should seldom or never need to wait for a write to occur" mean?
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Msg-id CAOg7f83vo1+Y3DMpu7317zgBwRZ2ZRow7VdphO7znm4AG=HJCA@mail.gmail.com
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Ответ на Re: What does "[backends] should seldom or never need to wait for a write to occur" mean?  (Bruce Momjian <bruce@momjian.us>)
Ответы Re: What does "[backends] should seldom or never need to wait for a write to occur" mean?
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Hi Bruce,

Thanks, yes I agree that that is much clearer. However when you say:

When the percentage of dirty shared buffers is high, the background writer writes some of them to the file system...

I haven't seen anything about a minimum percentage before the bgwriter kicks in, is that really the case? How is it configured?

Thanks, Chris.

On Wed, 11 Nov 2020 at 23:24, Bruce Momjian <bruce@momjian.us> wrote:
On Wed, Nov 11, 2020 at 11:29:09AM +0000, Chris Wilson wrote:
> I still believe that my original proposed change, to "This reduces the chances
> that a backend needing an empty buffer must [itself] write a dirty one back to
> disk before evicting it" (with one extra word added), resolves the ambiguity
> and also more clearly and directly focuses it on what the bgwriter does and
> why, making it better documentation. It might be incorrect if my understanding
> is incorrect - is it?

You make some very good points.  Here is an updated patch.

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  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

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