[LU-8709] parallel asynchronous readahead

• Type: Improvement
• Resolution: Duplicate
• Priority: Minor
• Affects Version/s: Lustre 2.10.0
• Labels: perf_optimization
• Assignee: Li Xi
• Reporter: Andreas Dilger

Description

Tracker for parallel async readahead improvement from DDN, as described in http://www.eofs.eu/_media/events/lad16/19_parallel_readahead_framework_li_xi.pdf

Note that it would be very desirable in the single thread case if the copy_to_user was also handled in parallel, as this is a major CPU overhead on many-core systems and if it can be parallelized it may increase the peak read performance.

As for lockahead integration with readahead, I agree that this is possible to do this, but it is only useful if the client doesn't get full-file extent locks. It would also be interesting if the write code detected sequential or strided writes and did lockahead at write time.

Issue Links

• is blocked by: LU-8726 Do fake read page on OST to help read performance benchmarking
• is duplicated by: LU-6 Update the readahead logic in lustre 2.0
• is related to: LU-8413 sanity test_101f fails with 'misses too much pages!'
• is related to: LU-8964 use parallel I/O to improve performance on machines with slow single thread performance
• is related to: LU-11416 Improve readahead for random read of small/medium files
• is related to: LU-12043 improve Lustre single thread read performances