On 06/27/2012 02:55 PM, Andrew Morton wrote: > On Wed, 27 Jun 2012 14:41:39 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote: > >> On 06/27/2012 02:12 PM, Andrew Morton wrote: >> >>> On Wed, 27 Jun 2012 11:09:31 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote: >>> >>>> On 06/27/2012 10:15 AM, Andrew Morton wrote: >>>> >>>>>> Considering mlock and CPU pinning >>>>>>> of realtime thread is very rare, it might be rather expensive solution. >>>>>>> Unfortunately, I have no idea better than you suggested. :( >>>>>>> >>>>>>> And looking 8891d6da17, mlock's lru_add_drain_all isn't must. >>>>>>> If it's really bother us, couldn't we remove it? >>>>> "grep lru_add_drain_all mm/*.c". They're all problematic. >>>> >>>> >>>> Yeb but I'm not sure such system modeling is good. >>>> Potentially, It could make problem once we use workqueue of other CPU. >>> >>> whut? >>> >>> My suggestion is that we switch lru_add_drain_all() to on_each_cpu() >>> and delete schedule_on_each_cpu(). No workqueues. >> >> >> Current problem is that RT thread doesn't yield his CPU so other tasks can't be scheduled in. >> schedule_on_each_cpu uses system workqueue so if there are any user to try using >> workqueue for the CPU(ex, schedule_work_on), he can make trouble, too. >> So my question is I doubt such greedy RT thread modeling is good. >> > > There's no way of fixing this without significantly degrading the > service which rt priority offers. As we don't wish to degrade that > service, schedule_work_on() and schedule_on_each_cpu() cannot be > implemented reliably. So we delete them. Okay. I'm not against strongly if local_irq_save/restore isn't expensive as a first step for removing them because I have no good idea. I want to add some comment on schedule_work_on and friends. "You shouldn't use it any more and we will try to remove this". Anyway, let's wait further answer, especially, RT folks. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>