On Wed, Jun 18, 2014 at 07:13:37PM -0700, Paul E. McKenney wrote:
> On Wed, Jun 18, 2014 at 06:42:00PM -0700, Andi Kleen wrote:
> >
> > I still think it's totally the wrong direction to pollute so
> > many fast paths with this obscure debugging check workaround
> > unconditionally.
>
> OOM prevention should count for something, I would hope.
>
> > cond_resched() is in EVERY sleeping lock and in EVERY memory allocation!
> > And these are really critical paths for many workloads.
> >
> > If you really wanted to do this I think you would first need
> > to define a cond_resched_i_am_not_fast() or somesuch.
> >
> > Or put it all behind some debugging ifdef.
>
> My first thought was to put it behind CONFIG_NO_HZ_FULL, but everyone
> seems to be enabling that one.
>
> As mentioned earlier, I could potentially push the check behind
> the need-resched check, which would get it off of the common case
> of the code paths you call out above.
Of course, it would also be good to measure this and see how much it
really hurts.
Thanx, Paul
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