On 6/28/22 7:00 PM, Ammar Faizi wrote: > On 6/29/22 7:50 AM, Alviro Iskandar Setiawan wrote: >> On Wed, Jun 29, 2022 at 7:28 AM Ammar Faizi wrote: >>> page_size = get_page_size(); >>> + if (page_size < 0) >>> + return page_size; >>> + >>> return rings_size(p, entries, cq_entries, page_size); >>> } >> >> the current error handling fallback to 4K if fail on sysconf(_SC_PAGESIZE): >> https://github.com/axboe/liburing/blob/68103b731c34a9f83c181cb33eb424f46f3dcb94/src/arch/generic/lib.h#L10-L19 >> with this patch, get_page_size() is only possible to return negative >> value on aarch64. > > Ah right, this one needs a revision. Either we fallback to 4K, or > return error if we fail. > >> i don't understand why the current master branch code fallback to 4K when fail? > > Neither do I. Maybe because 4K is widely used page size? > > Jens, can you shed some light on this? > > The current upstream does this: > > - For x86/x86-64, it's hard-coded to 4K. So it can't fail. > - For other archs, if sysconf(_SC_PAGESIZE) fails, we fallback to 4K. > > Now we are going to add aarch64, it uses a group of syscalls to get the page > size. So it may fail. What should we do when we fail? > > Fallback to 4K? Or return error code from syscall? 4k is the most common page size, by far, so makes sense to have that as a fallback rather than just error out. Perhaps the application will then fail differently, but there's also a chance that it'll just work. So I think just falling back to 4k if we fail for whatever reason is the sanest recourse. -- Jens Axboe
