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SubjectRe: Oprofile : need to adjust PC by 16 bytes
Andi Kleen a écrit :
> On Fri, Nov 14, 2008 at 04:25:51PM +0100, Eric Dumazet wrote:
>> Very strange results on my Intel E5450 CPU
>>
>> I found that I have to bias regs->ip by 16 bytes in order to have
>> correct profiling.
>
> Can you expand a bit how you determined if the profile is right or wrong?
>
> -Andi
>
>

opannotate -a vmlinux > FILE

And check results.

With the patch I get :

c041d270 <dst_release>: /* dst_release total: 16523 1.2978 */
252 0.0198 :c041d270: push %ebp
654 0.0514 :c041d271: test %eax,%eax
:c041d273: mov %esp,%ebp
47 0.0037 :c041d275: mov %eax,%edx
42 0.0033 :c041d277: je c041d289 <dst_release+0x19>
:c041d279: mov $0xffffffff,%eax
3 2.4e-04 :c041d27e: lock xadd %eax,0x80(%edx)
14766 1.1598 :c041d286: dec %eax
1 7.9e-05 :c041d287: js c041d28b <dst_release+0x1b>
53 0.0042 :c041d289: pop %ebp
705 0.0554 :c041d28a: ret
:c041d28b: mov $0x10e,%edx
:c041d290: mov $0xc0561ed5,%eax
:c041d295: call c022d1a0 <warn_on_slowpath>
:c041d29a: pop %ebp
:c041d29b: ret
:c041d29c: lea 0x0(%esi),%esi

This results please me : The cost is right after the "lock xadd" as expected.

Without patch, all addresses were off by 16 bytes.

On dst_release() it was on the call on warn_on_slowpath(),
and I am pretty sure it is not possible at all this WARN_ON is hit



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