Re: Dynamic switching of io_context

[Jens Axboe]

On Wed, Dec 17 2008, Vladislav Bolkhovitin wrote:
> >I haven't seen the rest of the code, so I may be wrong, but I suppose
> >that a better approach would be to use CLONE_IO to share io contexts,
> >if possible.
> 
> Unfortunately, it would be very non-optimal. As it is known, to achieve 
> the best performance with async. IO, it should be submitted by a limited 
> number of threads <= CPU count. So, the only way to submit IO from each 
> of, e.g. 100, clients in a dedicated per-client IO context is to 
> dynamically switch io_context of the current threads to io_context of 
> the client before IO submission.

There's also likely to be another use of exactly the same type of thing
- the acall patches from Zach. At least my vision of the punt-to-thread
approach would be very similar: grab an available thread and attach it
to a given IO context.

So while I did mention exactly what Fabio outlines in my initial mail on
this, a generic way to attach/detach IO contexts from processes/threads
would be useful outside of this project. nfsd comes to mind as well.

-- 
Jens Axboe

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