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SubjectRe: [PATCH 5/6] perf_counter: add more context information
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On Thu, 2009-04-02 at 20:18 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
> > On Thu, 2009-04-02 at 13:36 +0200, Ingo Molnar wrote:
> >
> > > > -#define MAX_STACK_DEPTH 255
> > > > +#define MAX_STACK_DEPTH 254
> > > >
> > > > struct perf_callchain_entry {
> > > > - u64 nr;
> > > > + u32 nr, hv, kernel, user;
> > > > u64 ip[MAX_STACK_DEPTH];
> > > > };
> >
> > Oh, and Paul suggested using u16s right after I send it out. So
> > I'll either send an update or send a incremental in case you
> > already applied it.
>
> yes, that's probably a good idea. Although u8 might be even better -
> do we ever want to do more than 256 deep stack vectors? Even those
> would take quite some time to construct and pass down.

We'd have to pad it with 4 more bytes to remain u64 aligned, also, why
restrict ourselves. That MAX_STACK_DEPTH limit is trivially fixable if
indeed someone finds its insufficient.





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