Re: O_NONBLOCK is NOOP on block devices

[M vd S]

On 3/10/10 2:21 PM, Jeff Moyer wrote:
> M vd S <mvds.00@xxxxxxxxx> writes:
>   
> > I also briefly tried aio_* and the libaio interface. The former is not
> > really asynchronous - all requests are put in one separate thread
> > where they will be executed in order, i.e. blocking, so you don't get
> > any advantage from NCQ or data that was cached by the disk or the
> > kernel. The latter apparently ends in an io_submit() which will block
> > until all queued reads are finished, but I might have missed something
> > there.
> >     
>
> What you missed is that the native aio system calls require O_DIRECT.
>   

Thanks, that made it work. It seems without O_DIRECT it's just like 
aio_* but without the separate thread. But I now get the "benefits" of 
O_DIRECT for free...

Cheers,
M.

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