[LU-15058] replace critical vmalloc allocations with kernel APIs to improve performance

• Type: Improvement
• Resolution: Unresolved
• Priority: Major
• Affects Version/s: Lustre 2.15.0
• Environment: Any client or server running Lustre.
• Assignee: James A Simmons
• Reporter: James A Simmons

Description

When memory allocation grow top large the method of allocation moves from kmalloc to vmalloc. Using vmalloc() uses global locking which greatly degrades performance. For ORNL we ended up preventing users form creating files stripped greater than 512. This problem impact very large RPC and other components of Lustre. The solution is to use the generic_radix work present in newer kernel developed for this very issue.

Issue Links

• is duplicated by: LU-15606 sanity-quota test_8: osc_brw_prep_request()) ASSERTION( i == 0 || pg->off > pg_prev->off ) failed
• is related to: LU-14469 lmv_rmfid() does 128K kmalloc()
• is related to: LU-13212 Lustre client hangs machine under memory pressure