* Gleb Natapov <gleb@xxxxxxxxxx> wrote: > On Mon, Nov 02, 2009 at 10:22:14AM +0100, Ingo Molnar wrote: > > > > * Gleb Natapov <gleb@xxxxxxxxxx> wrote: > > > > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > > > index f4cee90..14707dc 100644 > > > --- a/arch/x86/mm/fault.c > > > +++ b/arch/x86/mm/fault.c > > > @@ -952,6 +952,9 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code) > > > int write; > > > int fault; > > > > > > + if (arch_handle_page_fault(regs, error_code)) > > > + return; > > > + > > > > This patch is not acceptable unless it's done cleaner. Currently we > > already have 3 callbacks in do_page_fault() (kmemcheck, mmiotrace, > > notifier), and this adds a fourth one. Please consolidate them into a > > single callback site, this is a hotpath on x86. > > > This call is patched out by paravirt patching mechanism so overhead > should be zero for non paravirt cases. [...] arch_handle_page_fault() isnt upstream yet - precisely what is the instruction sequence injected into do_page_fault() in the patched-out case? > [...] What do you want to achieve by consolidate them into single > callback? [...] Less bloat in a hotpath and a shared callback infrastructure. > [...] I mean the code will still exist and will have to be executed on > every #PF. Is the goal to move them out of line? The goal is to have a single callback site for all the users - which call-site is patched out ideally - on non-paravirt too if needed. Most of these callbacks/notifier-chains have are inactive most of the time. I.e. a very low overhead 'conditional callback' facility, and a single one - not just lots of them sprinkled around the code. Ingo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
