On Sat, Aug 10, 2013 at 08:42:58AM -0700, Linus Torvalds wrote: > On Fri, Aug 9, 2013 at 4:04 PM, Andi Kleen <a...@firstfloor.org> wrote: > > From: Andi Kleen <a...@linux.intel.com> > > > > Move the cond_resched() check for CONFIG_PREEMPT_VOLUNTARY into > > the low level copy_*_user code. This avoids some code bloat and > > makes check much more efficient by avoiding unnecessary function calls. > > May I suggest going one step further, and just removing the > cond_resched() _entirely_, leaving just the debug test? > > There really is zero reason for doing a cond_resched() for user > accesses. If they take a page fault, then yes, by all means do that > (and maybe we should add one to the page fault trap if we don't have > it already), but without a page fault they really aren't that > expensive. > > We do many more expensive things without any cond_resched(), and doing > that cond_resched() really doesn't make much sense *unless* there's a > big expensive loop involved. > > Most of this series looks fine, but I really think that we > could/should just take that extra step, and say "no, user accesses > don't imply that we need to check for scheduling". > > Linus
In fact we are doing exactly this since 3.11-rc1. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
