Re: Is user-space AIO dead?

[Kenny Simpson]

--- David Lloyd <dmlloyd@xxxxxxx> wrote:

> On Wed, 11 Jan 2006, Kenny Simpson wrote:
> 
> > --- David Lloyd <dmlloyd@xxxxxxx> wrote:
> >> Wouldn't nonblocking I/O on regular files be nice?
> >
> > Yes it could be.  As I understand it, regular file writes (not O_DIRECT) 
> > are only to the page cache and only block when there is memory pressure 
> > (so it is more of a throttle).
> 
> If you were however using O_DIRECT or O_SYNC, you would then have a 
> mechanism to know when your writes have made it to disk, which might be 
> useful for transactional systems.

Right, but I'm not sure O_DIRECT implies stable storage, only data sent out to the device, not
held up in the page cache (I could be wrong).

AIO is implemented for O_DIRECT according to the paper, but they observed it not having benefit.

AIO being implemented to O_SYNC would be nice for my use, as it would also eliminate the extra
alignment restrictions brought on by O_DIRECT.

-Kenny


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