[LU-12518] improve Lustre unaligned IO read performances

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.14.0, Lustre 2.16.0
• Labels: IO500
• Assignee: Wang Shilong (Inactive)
• Reporter: Wang Shilong (Inactive)

Description

Currently, Lustre works well for aligned IO, but performance is pretty bad for unaligned IO stride read, we might need take some efforts to improve this situation.

One of the main problem with current stride read is it is based on Page Index, so if
we hit unaligned page case, Stride Read detection will not work well.

To support unaligned page stride read, we might change page index to bytes offset thus
stride read pattern detection work well and we won't hit many small pages RPC and readahead window reset.

At the same time, we shall keep as much as performances for existed cases and make
sure there won't be obvious regressions for aligned-stride and sequential read.

Issue Links

• is related to: LU-12043 improve Lustre single thread read performances