On Tue, Nov 1, 2022 at 2:37 PM Thomas Munro <thomas.mu...@gmail.com> wrote:
> Memory alignment patches: > > Direct I/O generally needs to be done to/from VM page-aligned > addresses, but only "standard" 4KB pages, even when larger VM pages > are in use (if there is an exotic system where that isn't true, it > won't work). We need to deal with buffers on the stack, the heap and > in shmem. For the stack, see patch 0001. For the heap and shared > memory, see patch 0002, but David Rowley is going to propose that part > separately, as MemoryContext API adjustments are a specialised enough > topic to deserve another thread; here I include a copy as a > dependency. The main direct I/O patch is 0003. One thing to note: Currently, a request to aset above 8kB must go into a dedicated block. Not sure if it's a coincidence that that matches the default PG page size, but if allocating pages on the heap is hot enough, maybe we should consider raising that limit. Although then, aligned-to-4kB requests would result in 16kB chunks requested unless a different allocator was used. -- John Naylor EDB: http://www.enterprisedb.com
