On Wed, 17 Jul 2013, Dave Hansen wrote: > On 07/17/2013 02:09 PM, Andrew Morton wrote: > > lock_page() is a pretty commonly called function, and I assume quite a > > lot of people run with CONFIG_DEBUG_VM=y. > > > > Is the overhead added by this patch really worthwhile? > > I always thought of it as a developer-only thing. I don't think any of > the big distros turn it on by default. That's how I think of it too (and the problem is often that too few mm developers turn it on); but Dave Jones did confirm last November that Fedora turns it on. I believe Fedora turns it on to help us all, and wouldn't mind a mere VM_BUG_ON(PageTail(page)) in __lock_page() if it's helpful to Kirill. But if VM_BUG_ONs become expensive, I do think it's for Fedora to turn off CONFIG_DEBUG_VM, rather than for mm developers to avoid it. Hugh -- 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>