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    SubjectRe: [PATCH 00/21] perf, c2c: Add new tool to analyze cacheline contention on NUMA systems
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    On Tue, Feb 11, 2014 at 12:02 PM, Peter Zijlstra <peterz@infradead.org> wrote:
    > On Tue, Feb 11, 2014 at 11:58:45AM +0100, Stephane Eranian wrote:
    >> On Tue, Feb 11, 2014 at 11:52 AM, Peter Zijlstra <peterz@infradead.org> wrote:
    >> > On Tue, Feb 11, 2014 at 11:35:45AM +0100, Stephane Eranian wrote:
    >> >> On Tue, Feb 11, 2014 at 8:14 AM, Peter Zijlstra <peterz@infradead.org> wrote:
    >> >> >
    >> >> > That blows; how much is missing?
    >> >>
    >> >> They need to annotate load and stores. I asked for that feature a while ago.
    >> >> It will come.
    >> >
    >> > And there is no way to deduce the information? We have type information
    >> > for all arguments and local variables, right? So we can follow that.
    >> >
    >> > struct foo {
    >> > int ponies;
    >> > int moar_ponies;
    >> > };
    >> >
    >> > struct bar {
    >> > int my_ponies;
    >> > struct foo *foo;
    >> > };
    >> >
    >> > int moo(struct bar *bar)
    >> > {
    >> > return bar->foo->moar_ponies;
    >> > }
    >> >
    >> > Since we have the argument type, we can find the type for both loads,
    >> > the first load:
    >> >
    >> > *bar+8, we know is: struct foo * bar::foo
    >> > *foo+4, we know is: int foo::moar_ponies
    >> >
    >> > Or am I missing something?
    >>
    >> How do you know that load at addr 0x1000 is accessing variable bar?
    >> The IP gives you line number, and then what?
    >> I think dwarf has the mapping regs -> variable and yes, the type info.
    >> But I am not sure that's enough.
    >
    > Ah, but if you have the instruction, you can decode it and obtain the
    > reg and thus type-info, no?
    >
    But on x86, you can load directly from memory, you'd only have the
    target reg for the load. Not enough.


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