Florian Weimer <fw@deneb.enyo.de> writes:

> * Goswin von Brederlow:
>
>> - The data is passed to libaio and needs to be kept alive and unmoved
>>   as long as libaio knows it.
>
> It also has to be aligned to a 512-byte boundary, so you can use
> O_DIRECT.  Linux does not support truely asynchronous I/O without
> O_DIRECT AFAIK, which rarely makes it worth the trouble.

True. But the libaio can provide a Aio.Buffer.make that returns an
aligned Bigarray (or string or whatever, currently a custom type).

If you write to files on a filesystem without O_DIRECT it will block
when submitting the requests till they have completed. Not sure what
happens on block devices without O_DIRECT.

My use case is for a Fuse Filesystem and writing to disks. O_DIRECT is
quite alright there. If you can't use O_DIRECT then you are left with
going multithreaded.

MfG
        Goswin