Re: Perf Reports Jump Instructions as Memory Access Instructions

[Andi Kleen <andi@xxxxxxxxxxxxxx>]

> > > 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.

-Andi