[LU-7085] Toward smaller memory allocations on wide-stripe file systems

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.8.0
• Affects Version/s: Lustre 2.8.0
• Environment: Test nodes with 2.7.57-gea38322
• Severity: 3
• Assignee: Yang Sheng
• Reporter: Matt Ezell

Description

I'm testing on a fairly recent master build that includes the patch from LU-6587 (refactor OBD_ALLOC_LARGE to always do kmalloc first). That band-aid has been great a improving performance on our wide-stripe file systems, but in the face of memory pressure/fragmentation, it will still rely on vmalloc to satisfy memory requests. Since users tend to use RAM, I'd like to see if there are any opportunities to reduce allocation sizes.

Anywhere we need to allocate sizeof(something) * num_stripes, we should check to see if there's any way to avoid per-stripe information or at least reduce sizeof(something).