Hi, I just noticed this item when I went through my TODO list today. I remember finding this issue a few months ago, but at that time, only bugs new to PG19 were being processed, so I put it on my TODO list.
This is a small issue, but it has been there for many years.
CalculateShmemSize() has logic to round size to a multiple of a typical page
size:
```
/* might as well round it off to a multiple of a typical page size */
size = add_size(size, 8192 - (size % 8192));
```
When size is already a multiple of 8192, this add_size() call is not needed; it
only results in an extra 8192 bytes being allocated in shared memory. The fix
is simple:
```
if (size % 8192 != 0)
/* might as well round it off to a multiple of a typical page
size */
size = add_size(size, 8192 - (size % 8192));
```
I put the comment within the if clause because I remember Tom once mentioning
that this would be the preferred style.
Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/
v1-0001-Avoid-extra-shared-memory-page-in-CalculateShmemS.patch
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