Details
-
Technical task
-
Resolution: Unresolved
-
Minor
-
None
-
Lustre 2.16.0
-
None
-
3
-
9223372036854775807
Description
With the addition of UDIO support on the client, there needs to be some interface to inform userspace applications about what alignment requirements exist for using DIO. OTHERWISE, they will get errors trying to submit unaligned DIO requests and either have to guess at the alignment (PAGE_SIZE, 4096-byte, 512-byte, 1-byte) or only use the largest possible alignment.
The statx() interface in newest kernels provides an interface to report the DIO alignment requirements on a per-file basis, and could be added to llite (even for older kernels, AFAIK). Ideally, this would also be backpirted to b2_15 to allow applications to start using this interface sooner (though it would only report PAGE_SIZE as the allowed alignment).