[LU-17630] osc_lru_shrink() should not block scheduling for long

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0
• Severity: 3
• Assignee: Alex Zhuravlev
• Reporter: Alex Zhuravlev

Description

osc_lru_shrink() can take quite long as the number of cached pages can be high. in such a case another threads may starve for CPU cycles and the kernel will be printing warnings:

Nov  9 03:11:25 foxtrot3 kernel: NMI watchdog: BUG: soft lockup - CPU#23 stuck for 22s! [ptlrpcd_01_10:3531]
...
Mar  1 14:03:47 woodbass46 kernel: Call Trace:
Mar  1 14:03:47 woodbass46 kernel: _raw_spin_lock+0x1c/0x20
Mar  1 14:03:47 woodbass46 kernel: osc_page_delete+0x2f2/0x470 [osc]
Mar  1 14:03:47 woodbass46 kernel: cl_page_delete0+0x71/0x1f0 [obdclass]
Mar  1 14:03:47 woodbass46 kernel: cl_page_delete+0x2a/0xf0 [obdclass]
Mar  1 14:03:47 woodbass46 kernel: discard_pagevec+0x6f/0x150 [osc]
Mar  1 14:03:47 woodbass46 kernel: osc_lru_shrink+0x80c/0x840 [osc]
Mar  1 14:03:47 woodbass46 kernel: lru_queue_work+0xee/0x220 [osc]
Mar  1 14:03:47 woodbass46 kernel: work_interpreter+0x32/0x110 [ptlrpc]
Mar  1 14:03:47 woodbass46 kernel: ptlrpc_check_set.part.29+0x41d/0x1e80 [ptlrpc]
Mar  1 14:03:47 woodbass46 kernel: ? __switch_to+0x183/0x480
Mar  1 14:03:47 woodbass46 kernel: ptlrpcd_check+0x3d5/0x5b0 [ptlrpc]
Mar  1 14:03:47 woodbass46 kernel: ptlrpcd+0x374/0x4b0 [ptlrpc]

Issue Links

• is related to: LU-16343 soft lockups ptlrpcd
• is related to: LU-18053 Add active osc_lru_shrink() limit