AIO Enabled?

[Ivan Klymenko]

On Tue, 29 Mar 2016 14:42:57 -0400
Rick Miller <vmiller at hostileadmin.com> wrote:

> Hi all,
> 
> I found old mail threads and blog posts (circa 2006 - 2010) that
> stated AIO is not enabled by default in FreeBSD.  However, when
> running strings on the kernel, it appears AIO bits may be available...
> 
> $ sudo strings -n3 /boot/kernel/kernel | grep -i aio
> aio_swake
> freebsd32_aio_read
> freebsd32_aio_write
> freebsd32_aio_return
> freebsd32_aio_suspend
> freebsd32_aio_cancel
> freebsd32_aio_error
> freebsd32_oaio_read
> freebsd32_oaio_write
> freebsd32_aio_waitcomplete
> freebsd32_aio_fsync
> freebsd32_aio_mlock
> AIOSTOP: bad channel 0x%x
> AIOSYNC chan 0x%03lx pos %lu unimplemented
> AIONWRITE
> AIOGSIZE
> AIOSSIZE
> AIOGFMT
> AIOSFMT
> AIOGMIX
> AIOSMIX
> AIOSTOP
> AIOSYNC
> AIOGCAP
> nfsaio
> aio_prio_delta_max
> aio_max
> aio_listio_max
> 
> aio(4) states it can be linked in the kernel using options VFS_AIO or
> dynamically using loader.conf or kldload suggesting it still is not
> enabled by default.  This brings me to a couple questions I hope are
> easily answered.
> 
> 1) Is AIO still disabled by default in FreeBSD 10.x and newer?
> 2) Does strings send the same output above to STDOUT irregardless of
> whether AIO is enabled/disabled?
> 
> 
> Thanks.
> 

for CURRENT
/usr/src/UPDATING
...
20160301:
        The AIO subsystem is now a standard part of the kernel.  The
        VFS_AIO kernel option and aio.ko kernel module have been removed.
        Due to stability concerns, asynchronous I/O requests are only
        permitted on sockets and raw disks by default.  To enable
        asynchronous I/O requests on all file types, set the
        vfs.aio.enable_unsafe sysctl to a non-zero value.
...