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SubjectRe: [PATCH] perf, x86: Disable sanity check
On 4/18/12 10:22 PM, Frederic Weisbecker wrote:

> So rbp is part of the JIT stack but not rsp?
> Do you have a practical example of that? I must confess I don't know
> much about JIT stack.

Nothing specific to JITs here. Any time an app has two stacks S1 and S2
(with S1 at a lower address and S2 at a higher address) and %rsp at the
time of a perf event is pointing to S2, we don't get traces beyond S2.

| |
| |
| 0x1000000 | <-- %rbp
| |
| |
S2: 0x2000000 | | <-- %rsp
| |
| |
| |
| frame3 |
| |
| frame2 |
| |
S1: 0x1000000 | frame1 |
| |
| |
| |
| |

gdb is able to show:

(gdb) bt
<frame at 0x2000000>
frame1
frame2
frame3
frame4
..

just fine.

In our use case, there may be multiple transitions between S1 and S2.
For eg: frame4 could be on S2 (i.e 0x2xxxxxx range).

-Arun


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