Re: introduce dynamic shared memory registry

On 18/12/2023 13:39, Andrei Lepikhov wrote:
> On 5/12/2023 10:46, Nathan Bossart wrote:
>> I don't presently have any concrete plans to use this for anything, but I
>> thought it might be useful for extensions for caching, etc. and wanted to
>> see whether there was any interest in the feature.
>
> I am delighted that you commenced this thread.
> Designing extensions, every time I feel pain introducing one shared
> value or some global stat, the extension must be required to be loadable
> on startup only. It reduces the flexibility of even very lightweight
> extensions, which look harmful to use in a cloud.

After looking into the code, I have some comments:
1. The code looks good; I didn't find possible mishaps. Some proposed
changes are in the attachment.
2. I think a separate file for this feature looks too expensive.
According to the gist of that code, it is a part of the DSA module.
3. The dsm_registry_init_or_attach routine allocates a DSM segment. Why
not create dsa_area for a requestor and return it?

--
regards,
Andrei Lepikhov
Postgres Professional