Proposal: Limitations of palloc inside checkpointer

Hi, hackers!

Historically, the checkpointer process use palloc() into
AbsorbSyncRequests() function. Therefore, the checkpointer does not
expect to receive a request larger than 1 GB.

We encountered a case where the database went into recovery state, after
applying all wal, the checkpointer process generated an "invalid memory
alloc request size" error and entered a loop. But it is quite acceptable
for the recovery state to receive such a large allocation request.

A simple solution to this problem is to use palloc_extended() instead of
palloc(). But is it safe to allow the checkpointer to allocate so much
memory at once?

I have proposal to update this memory allocation but I need your ideas
and advices on how to do it in appropriate way. As an idea, we can
replace the array with a list of arrays to allocate memory in chunks. As
a bad idea, we can process a temporary array without locking.

I would be glad to hear your ideas and suggestions about this topic.
Have a nice day!

--
Ekaterina Sokolova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company