On Wed 13-01-21 19:11:06, Muchun Song wrote: > On Wed, Jan 13, 2021 at 6:38 PM Michal Hocko <mhocko@xxxxxxxx> wrote: [...] > > > I just want the fix patch to be small enough. > > > So I do the retry in this patch. If you do not agree with this. I > > > will fold this into the previous patch. > > > > > > Do you mean this? > > > > > > cpu_relax(); > > > cond_resched(); > > > cpu_relax(); > > > > No, I am questiong the use of cpu_relax. What is the point? > > If there is no task to be scheduled. Here is just a while loop. > The cpu_relax is a good thing to insert into busy-wait loops, > right? Well in an ideal world we would simply have a way to block and wait for the particular page. This is probably an overkill for a rare event like this. And while you are right that theoretically there might be nobody else to run but I find it rather unlikely considering that this path is racing with somebody. Sure there is even less likely possibility that the race is actually waiting for worker context but really I would just make it simple retry loop. If we ever hit a real busy loop then this would be pretty straightforward to spot and fix up. It's not like I am against the patch with cpu_relax but I find it excessive for this purpose. If you feel strongly then just keep it. Once the two patches are squashed I will ack it. -- Michal Hocko SUSE Labs
