From owner-freebsd-stable@freebsd.org  Tue Mar 21 16:42:31 2017
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Date: Tue, 21 Mar 2017 19:42:27 +0300
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: stable@freebsd.org
Subject: Lock contention in AIO
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I am see lock contetntion cuased by aio read (same file segment from
multiple process simultaneous):

07.74%  [26756]    lock_delay @ /boot/kernel/kernel
 92.21%  [24671]     __mtx_lock_sleep
  52.14%  [12864]      vm_page_enqueue
   100.0%  [12864]       vm_fault_hold
    87.71%  [11283]        vm_fault_quick_hold_pages
     100.0%  [11283]         vn_io_fault1
      100.0%  [11283]          vn_io_fault
       99.88%  [11270]           aio_process_rw
        100.0%  [11270]            aio_daemon
         100.0%  [11270]             fork_exit
       00.12%  [13]              dofileread
        100.0%  [13]               kern_readv

Is this know problem?