Re: show size of DSAs and dshash tables in pg_dsm_registry_allocations
| От | Rahila Syed |
|---|---|
| Тема | Re: show size of DSAs and dshash tables in pg_dsm_registry_allocations |
| Дата | |
| Msg-id | CAH2L28sQwRPd1oAddG3NGFDC7xRsvO7xLrvqptm_eVirFGqhqQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: show size of DSAs and dshash tables in pg_dsm_registry_allocations (Nathan Bossart <nathandbossart@gmail.com>) |
| Ответы |
Re: show size of DSAs and dshash tables in pg_dsm_registry_allocations
|
| Список | pgsql-hackers |
Hi,
The patch LGTM overall. I had tested the v1 and it worked fine.
That function was added by commit ee1b30f, which AFAICT used an exclusive
lock just to stay consistent with the rest of dsa.c [0]. I don't see any
discussion about this in the original DSA thread [1]. Perhaps we could go
through dsa.c and switch to LW_SHARED where appropriate, although I doubt
it makes much difference.
Thank you for highlighting the discussions. I'm unsure about the best
approach here, but I think it would be safe to stay consistent with the
rest of the code in dsa.c, especially since it's unclear that the use of
LW_EXCLUSIVE for reading values in dsa is a mistake.
> +size_t
> +dsa_get_total_size_from_handle(dsa_handle handle)
>
> I believe this function will report the size as long as the dsa control
> structure is created within a dsm segment, since all dsm segments are
> tracked by the global list - dsm_segment_list, regardless of whether the
> dsa is created with dsa_create or dsa_create_in_place. In that case,
> perhaps we should update the comment above to reflect this.
Sorry, I'm not following what you think we should update the comment to
say.
Sorry for the confusion, I am trying to say that we can change the
following comment
+ *The area must have
+ * been created with dsa_create (not dsa_create_in_place).
to say this:
"The area must have been created using dsm_segments"
Since, this function can report the size of an area created with dsa_create_in_place
too, as long as the area is created using dsm_segments.
too, as long as the area is created using dsm_segments.
> 4. Since, with this change, the size column will show memory allocation
> regardless of whether it is currently mapped in the local process, I
> think it would be helpful to add a boolean column to display the mapped
> status as a future enhancement.
Maybe, although I'm struggling to think of a scenario where that
information would be useful.
Fair enough. I was thinking of a scenario where a user might want
to see how much dsa memory is allocated in the client backend process.
However, I understand now that this view is designed for the entire cluster,
and adding a column which is process-specific could lead to confusion.
Thank you,
Rahila Syed
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