Re: [PATCH v8 1/7] perf/core: Define the common branch type classification

[Jin, Yao]

Sure, thanks so much!


On 7/13/2017 8:04 PM, Michael Ellerman wrote:
> Jin Yao <yao.jin@xxxxxxxxxxxxxxx> writes:
>
> > It is often useful to know the branch types while analyzing branch
> > data. For example, a call is very different from a conditional branch.
> >
> > Currently we have to look it up in binary while the binary may later
> > not be available and even the binary is available but user has to take
> > some time. It is very useful for user to check it directly in perf
> > report.
> >
> > Perf already has support for disassembling the branch instruction
> > to get the x86 branch type.
> >
> > To keep consistent on kernel and userspace and make the classification
> > more common, the patch adds the common branch type classification
> > in perf_event.h.
> >
> > The patch only defines a minimum but most common set of branch types.
> >
> > PERF_BR_UNKNOWN         : unknown
> > PERF_BR_COND            ïconditional
> > PERF_BR_UNCOND          : unconditional
> > PERF_BR_IND             : indirect
> > PERF_BR_CALL            : function call
> > PERF_BR_IND_CALL        : indirect function call
> > PERF_BR_RET             : function return
> > PERF_BR_SYSCALL         : syscall
> > PERF_BR_SYSRET          : syscall return
> > PERF_BR_COND_CALL       : conditional function call
> > PERF_BR_COND_RET        : conditional function return
> >
> > The patch also adds a new field type (4 bits) in perf_branch_entry
> > to record the branch type.
> >
> > Since the disassembling of branch instruction needs some overhead,
> > a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it
> > needs to disassemble the branch instruction and record the branch
> > type.
> Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (powerpc)
>
> If you like.
>
> cheers