Re: Perf Reports Jump Instructions as Memory Access Instructions

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Thanks! This seems reasonable. But as Arnaldo says, why is there a skid in the access address while PEBS is used? Both RIP and Access Address should match, Right?

On 2020-05-26 21:12, Andi Kleen wrote:

The access point is at offset 0 of the following disassembly:
> Dump of assembler code for function cairo_surface_get_device_scale@plt:

0x000000000002a310 <+0>:     jmpq   *0x2c8b3a(%rip)        # 0x2f2e50
0x000000000002a316 <+6>:     pushq  $0x1c7
0x000000000002a31b <+11>:    jmpq   0x28690

This is an unconditional jump which will not lead to macrofusion.

But that will access memory, no? The instruction at offset 0.
Instruction fetches are not sampled by the MEM_INST_RETIRED event.

This is an indirect jump through memory, so it accesses the memory at
0x2c8b3a(%rip). These kind of accesses are sampled by the event.

Other memory accesses as part of other instructions may be sampled too.


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