On Tue, Jun 16, 2009 at 10:09:24AM +0200, Ingo Molnar wrote:
>
> * Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
>
> > > @@ -43,11 +44,19 @@ static int full_paths;
> > > static unsigned long page_size;
> > > static unsigned long mmap_window = 32;
> > >
> > > +struct ip_chain_event {
> > > + __u16 nr;
> >
> > Is it needed to have the nr encoded in the ip_chain? We can
> > already find it by doing kernel + user.
>
> That's a good observation. Since we havent exposed the call-chain
> bits in upstream version of the tools, we could still improve on
> this a little bit.
>
> I think the best would be context separators which occupy a special
> address in some quiet corner of the 64-bit address space.
>
> That way we'd have streams of u64 entries:
>
> ip-1
> ip-2
> CONTEXT_IRQ
> ip-3
> ip-4
> CONTEXT_SYSCALL
> ip-5
> ip-6
>
> The following contexts IDs would be useful:
>
> CONTEXT_NMI
> CONTEXT_HARDIRQ
> CONTEXT_SOFTIRQ
> CONTEXT_KERNEL
> CONTEXT_USER
> CONTEXT_GUEST_NMI
> CONTEXT_GUEST_HARDIRQ
> CONTEXT_GUEST_SOFTIRQ
> CONTEXT_GUEST_KERNEL
> CONTEXT_GUEST_USER
>
> The context IDs would occupy some rare and
> unlikely-to-be-allocated-soon corner of the address space - say
> startig at 0x8765432112345000. (and real RIPs would be filtered and
> nudged just outside that space of a handful IDs.)
>
> The advantage would be that this is infinitely flexible and
> extensible - any level of nesting can be expressed without having
> separate fields for nr_hv_guest_irq, etc. It's also pretty fast to
> parse.
Indeed, nice idea!
> Hm?
>
> Ingo
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