On Mon, Nov 27, 2017 at 02:27:20PM +0800, jiang.biao2@xxxxxxxxxx wrote:> > I agree with your concern. How about we take another way by
> > adding some warning in such case? such as,
> > freeable = shrinker->count_objects(shrinker, shrinkctl);
> > + if (unlikely(freeable < 0)) {
> > + pr_err("shrink_slab: %pF negative objects returned. freeable=%ld\n",
> > + shrinker->scan_objects, freeable);
> > + freeable = 0; //maybe not needed?
> > + }
> > if (freeable == 0)
> > return 0;
> > In this way, we would not break the API, but could alert user exception
> > with message, and make it more robust in such case.
>
> True but it would be a problem robust vs. effectivess tradeoff.
> Think about that everyone want to make thier code robust.
> It means they start to dump lots of defensive code so code start
> to look like complicated as well as binary bloating.
> So, whenever we add some more, we should think how effective
> the code I am putting?
>
> In this case, I'm skeptical, Sorry. But others might have different
> opinions. :)
With all due respect. I still think the robustness is more important than
effectiveness in this case. :)
First, the minus value could break all the following procedure in
do_shrink_slab which may lead to long time looping on
*tight on memory* situations.
Second, there is *unlikely* macro to minimize the cost.
Third, there is already similar procedure for *total_scan < 0*.
Last, it did happen in my scenario and maybe happen in other
unexpected situations.
Just my personal option, thanks a lot for you reply and explanation. :)
Regards,
