On 12.08.21 16:18, Julien Rouhaud wrote:
On Thu, Aug 12, 2021 at 9:34 PM Peter Eisentraut
<peter.eisentr...@enterprisedb.com> wrote:
On 27.02.21 09:08, Julien Rouhaud wrote:
PFA a patch that fixes pg_prewarm and pg_stat_statements explicit alignment to
CACHELINEALIGN, and also update the alignment in hash_estimate_size() to what I
think ShmemInitHash will actually consume.
For extensions, wouldn't it make things better if
RequestAddinShmemSpace() applied CACHELINEALIGN() to its argument?
If you consider the typical sequence of RequestAddinShmemSpace(mysize())
and later ShmemInitStruct(..., mysize(), ...),
But changing RequestAddinShmemSpace() to apply CACHELINEALIGN() would
only really work for that specific usage only? If an extension does
multiple allocations you can't rely on correct results.
I think you can do different things here to create inconsistent results,
but I think there should be one common, standard, normal,
straightforward way to get a correct result.
Btw., I think your patch was wrong to apply CACHELINEALIGN() to
intermediate results rather than at the end.
I'm not sure why you think it's wrong. It's ShmemInitStruct() that
will apply the padding, so if the extension calls it multiple times
(whether directly or indirectly), then the padding will be added
multiple times. Which means that in theory the extension should
account for it multiple time in the amount of memory it's requesting.
Yeah, in that case it's probably rather the case that there is one
CACHELINEALIGN() too few, since pg_stat_statements does two separate
shmem allocations.
