Re: Enhancing Memory Context Statistics Reporting

Hi,

Please find attached the updated patches after some cleanup and test
fixes.

Thank you,
Rahila Syed

On Tue, Feb 18, 2025 at 6:35 PM Rahila Syed <rahilasyed90@gmail.com> wrote:

> Hi,
>
>>
>> Thanks for updating the patch!
>>
>> The below comments would be a bit too detailed at this stage, but I’d
>> like to share the points I noticed.
>>
>> Thanks for sharing the detailed comments. I have incorporated some of them
> into the new version of the patch. I will include the rest when I refine
> and
> comment the code further.
>
> Meanwhile, I have fixed the following outstanding issues:
>
> 1.  Currently one DSA  is created per backend when the first request for
>> statistics is made and remains for the lifetime of the server.
>> I think I should add logic to periodically destroy DSAs, when memory
>> context statistics are not being *actively* queried from the backend,
>> as determined by the statistics timestamp.
>>
>
> After an offline discussion with Andres and Tomas, I have fixed this to
> use
> only one DSA for all the publishing backends/processes. Each backend
>  allocates smaller chunks of memory within the DSA while publishing
> statistics.
> These chunks are tracked independently by each backend, ensuring that two
> publishing backends/processes do not block each other despite using the
> same
> DSA. This approach eliminates the overhead of creating multiple DSAs,
> one for each backend.
>
> I am not destroying the DSA area because it stores the previously
> published
> statistics for each process. This allows the system to display older
> statistics
> when the latest data cannot be retrieved within a reasonable time.
> Only the most recently updated statistics are kept, while all earlier ones
> are freed using dsa_free by each backend when they are no longer needed.
> .
>
>> 2. The two issues reported by Fujii-san here: [1].
>> i. I have proposed a fix for the first issue here [2].
>> ii. I am able to reproduce the second issue. This happens when we try
>> to query statistics of a backend running infinite_recurse.sql. While I am
>> working on finding a root-cause, I think it happens due to some memory
>> being overwritten due to to stack-depth violation, as the issue is not
>> seen
>> when I reduce the max_stack_depth to 100kb.
>>  }
>>  }
>>
>
> The second issue is also resolved by using smaller allocations within a
> DSA.
> Previously, it occurred because a few statically allocated strings were
> placed
> within a single large chunk of DSA allocation. I have changed this to use
> dynamically allocated chunks with dsa_allocate0 within the same DSA.
>
> Please find attached updated and rebased patches.
>
> Thank you,
> Rahila Syed
>