On 24.02.26 12:28, Bertrand Drouvot wrote:
You can/should use C11 standard alignas(), so you don't need to worry about
whether it's supported or not.
Oh right, I did not notice 300c8f53247 and following like e7075a3405c,
d4c0f91f7d5
and 97e04c74bed.
PFA, 0001 doing so for PGPROC and PgAioUringContext. As those are typedef,
the patch puts alignas within the struct.
For PGPROC at the start of the struct, I think that placing it on the first
member
is the right location because it ensures the whole struct is aligned to
PG_CACHE_LINE_SIZE
without adding padding before this member. For example if I set it on
backendType,
then it adds 100 bytes of padding and the struct is obviously still a multiple
of
PG_CACHE_LINE_SIZE but is now 1024 bytes (instead of 896).
For PgAioUringContext at completion_lock (like suggested by Andres in [1]),
which
is also the start of the struct.
I checked and the padding for those are exactly the same after the changes.
I have committed the 0001 patch.
0002, is also making use of alignas in ItemPointerData, but this one is more
tricky so I'm not sure that's worth it (given the fact that we still need to
keep pg_attribute_aligned() as explained by Peter in [2]).
This doesn't seem worth it to me. Let's skip it.
