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SubjectRE: aio is unlikely
Date

Andrew Morton wrote:
> aio is unlikely
> Stick an unlikely() around is_aio(): I assert that most IO is
synchronous.
>
> -#define in_aio() !is_sync_wait(current->io_wait)
> +#define in_aio() (unlikely(!is_sync_wait(current->io_wait)))

> Jeff Garzik <jeff@garzik.org> wrote:
>
> > > -#define in_aio() !is_sync_wait(current->io_wait)
> > > +#define in_aio() (unlikely(!is_sync_wait(current->io_wait)))
> >
> > Please revert. Workload-dependent "likelihood" should not cause
> > programmers to add such markers.
> a) disagree with the above
>
> b) if in_aio() ever returns true we do
>
> printk(KERN_ERR "%s(%s:%d) called in async context!\n",
> __FUNCTION__, __FILE__, __LINE__);
>
> so I sure hope it's unlikely for all workloads.

Shouldn't unlikely() go where in_aio() is actually used, if we printk(error)
there?
Isn't putting likely/unlikely into a boolean function-like macro itself
asking for later trouble?

--Alex.


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