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help / color / mirror / Atom feedFrom: Michael Paquier <[email protected]>
To: Magnus Hagander <[email protected]>
Cc: Nathan Bossart <[email protected]>
Cc: Bossart, Nathan <[email protected]>
Cc: Fujii Masao <[email protected]>
Cc: Justin Pryzby <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Mark Dilger <[email protected]>
Cc: Don Seiler <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: Estimating HugePages Requirements?
Date: Tue, 26 Apr 2022 10:34:06 +0900
Message-ID: <YmdMDiCCyVJLlB/[email protected]> (raw)
In-Reply-To: <CABUevEyD_aLM=oXi1jj8hRN=7aJq--jN4FP+ehY8Vu60+QH61A@mail.gmail.com>
References: <20220314173417.GA1020555@nathanxps13>
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<20220315224439.GA1133771@nathanxps13>
<[email protected]>
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On Mon, Apr 25, 2022 at 04:55:25PM +0200, Magnus Hagander wrote:
> AIUI that was the original use-case for this feature. It certainly was for
> me :)
Perhaps we'd be fine with relaxing the requirements here knowing that
the control file should never be larger than PG_CONTROL_MAX_SAFE_SIZE
(aka the read should be atomic so it could be made lockless). At the
end of the day, to be absolutely correct in the shmem size estimation,
I think that we are going to need what's proposed here or the sizing
may not be right depending on how extensions adjust GUCs after they
load their _PG_init():
https://www.postgresql.org/message-id/20220419154658.GA2487941@nathanxps13
That's a bit independent, but not completely unrelated either
depending on how exact you want your number of estimated huge pages to
be. Just wanted to mention it.
>> Contrary to Linux, we don't need to care about the number of large
>> pages that are necessary because there is no equivalent of
>> vm.nr_hugepages on Windows (see [1]), do we? If that were the case,
>> we'd have a use case for huge_page_size, additionally.
>
> Right, for this one in particular -- that's what I meant with my comment
> about there not being a limit. But this feature works for other settings as
> well, not just the huge pages one. Exactly what the use-cases are can
> vary, but surely they would have the same problems wrt redirects?
Yes, the redirection issue would apply to all the run-time GUCs.
--
Michael
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Subject: Re: Estimating HugePages Requirements?
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