Messages in this thread | | | Date | Wed, 20 Oct 2010 11:27:45 -0400 | From | Jason Baron <> | Subject | Re: [PATCH] tracing: Cleanup the convoluted softirq tracepoints |
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On Tue, Oct 19, 2010 at 07:05:15PM -0400, Steven Rostedt wrote: > On Tue, 2010-10-19 at 15:49 -0700, H. Peter Anvin wrote: > > On 10/19/2010 03:41 PM, Mathieu Desnoyers wrote: > > >> > > >> OK, first of all, there are some serious WTFs here: > > >> > > >> # define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t" > > >> > > >> A jump instruction is one of the worst possible NOPs. Why are we doing > > >> this? > > > > > > This code is dynamically patched at boot time (and module load time) with a > > > better nop, just like the function tracer does. > > > > > > > That's just ridiculous... start out with something sane and you at least > > have the chance of not having to patch it. > > Yep we can fix this. Jason? >
sure. The idea of the 'jmp 0' was simply to be an lcd for x86, if there's a better lcd for x86, I'll update it. But note, that since the 'jmp 0' is patched to a better nop at boot, we wouldn't see much gain. And in the boot path we are using 'text_poke_early()', so avoiding that isn't going to improve things much.
I've got a few fixup patches in the queue that I'm going to post first, and then I'll take a look at this change.
thanks,
-Jason
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