Re: fio-2.1.4 - dlopen failed for libaio

[Jens Axboe <axboe@kernel.dk>]

On 09/05/2014 07:42 AM, Matthew Weber wrote:
> Status output from a case where fio is built without libaio support....
>      fio: engine libaio not loadable
>      fio: failed to load engine libaio
>      fio: file:ioengines.c:102, func=dlopen, error=libaio: cannot open
> shared object file: No such file or directory
> 
> I don't think this is necessarily a bug, but I wanted to comment on
> what we observed.  There was some discussion on this on the buildroot
> mailing list since we thought we needed to force a dependency on
> having libaio always built as a dependency for the fio package to link
> against.  Instead the user just needs to enable the libaio if they use
> it as an engine (which is fine).
> http://buildroot-busybox.2317881.n4.nabble.com/PATCH-v4-fio-add-missing-libaio-dependency-td77314.html
> 
> Here our interpretation of what's happening.... It looks like the
> shared library open error is one of the expected failure outputs if
> you don't have support for the specific dynamic "io library".  The
> build of the fio package does correctly determine if the libaio lib is
> present or not and correctly adds it to the ioengines list for use (at
> build time, so the enghelp output is correct, etc).  However when fio
> is executed, it looks up if a "set of operations" is registered for
> whichever ioengine library used.  If they are, it goes ahead and uses
> them.  If they need to be loaded, like in the case of libaio, it
> attempts to load them. However there is no check to see if fio was
> built with support for the external library being loaded (like in this
> case of libaio).

The output could be improved, but it's expected behavior. If you specify
ioengine=someengine, fio will check for an internal engine of that name.
If it doesn't find one, it will attempt to dynamically load an engine
with that file name. When that then fails, you get the above output.
This is no different than if you did ioengine=windowsaio on Linux, or
ioengine=libaio on Windows, for instance.

-- 
Jens Axboe