[LU-12071] bypass pagecache for large files

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.14.0
• Assignee: Alex Zhuravlev
• Reporter: Alex Zhuravlev

Description

pagecache invalidation is quite expensive:

pagecache enabled:

ost  1 sz 268435456K rsz 16384K obj   16 thr   64 write 5094.16 [2287.82, 6383.46] read 5295.85 [5039.42, 5567.47] 

pagecache disabled:

ost  1 sz 268435456K rsz 16384K obj   16 thr   64 write 4460.22 [3615.59, 5151.63] read 5218.00 [4847.41, 5551.34] 

we do already have a mechanism to bypass pagecache in place, just need to use that properly.

Issue Links

• is duplicated by: LU-11341 Do not use pagecache for I/O
• is duplicated by: LU-12346 ladvise willread should work even if OSD cache is disabled
• is related to: LU-12016 sanity: test_156 Error: ''IN CACHE: before: 8255, after: 8258''
• is related to: LU-13680 large allocations in osd_bufs_get() failing
• is related to: LU-12179 allocate continuous pages when disabled page caches
• is related to: LU-410 Performance concern with Shrink file_max_cache_size to alleviate the memory pressure of OST patch for LU-15
• is related to: LU-11347 Do not use pagecache for SSD I/O when read/write cache are disabled