linux-kernel - Re: [PATCH v6 1/7] perf/core: Define the common branch type classification

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Date:   Mon, 10 Jul 2017 21:28:39 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>, acme@...nel.org,
        jolsa@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, kan.liang@...el.com,
        ak@...ux.intel.com, linuxppc-dev@...ts.ozlabs.org,
        Linux-kernel@...r.kernel.org, yao.jin@...el.com
Subject: Re: [PATCH v6 1/7] perf/core: Define the common branch type
 classification

Hi,

Following branch types should be common enough, right?

+	PERF_BR_COND		= 1,	/* conditional */
+	PERF_BR_UNCOND		= 2,	/* unconditional */
+	PERF_BR_IND		= 3,	/* indirect */
+	PERF_BR_CALL		= 4,	/* call */
+	PERF_BR_IND_CALL	= 5,	/* indirect call */
+	PERF_BR_RET		= 6,	/* return */

I decide to only define these types in this patch set. For other more 
arch-related branch type, we can add it in future.

Is this OK?

Thanks
Jin Yao

On 7/10/2017 9:10 PM, Segher Boessenkool wrote:
> Hi!
>
> On Mon, Jul 10, 2017 at 07:46:17PM +0800, Jin, Yao wrote:
>> 1. We all agree these definitions:
>>
>> +	PERF_BR_COND		= 1,	/* conditional */
>> +	PERF_BR_UNCOND		= 2,	/* unconditional */
>> +	PERF_BR_IND		= 3,	/* indirect */
>> +	PERF_BR_CALL		= 4,	/* call */
>> +	PERF_BR_IND_CALL	= 5,	/* indirect call */
>> +	PERF_BR_RET		= 6,	/* return */
>> +	PERF_BR_SYSCALL		= 7,	/* syscall */
>> +	PERF_BR_SYSRET		= 8,	/* syscall return */
>> +	PERF_BR_IRET		= 11,	/* return from interrupt */
> Do we?  It does not map very well to PowerPC branch types.
>
>> 2. I wish to keep following definitions for x86.
>>
>> +	PERF_BR_IRQ		= 9,	/* hw interrupt/trap/fault */
>> +	PERF_BR_INT		= 10,	/* sw interrupt */
>>
>> PERF_BR_INT is triggered by instruction "int" .
>> PERF_BR_IRQ is triggered by interrupts, traps, faults (the ring 0,3
>> transition).
> So your "PERF_BR_INT" is a system call?  And PERF_BR_IRQ is not an
> interrupt request (as its name suggests), not what we call an "external
> interrupt" either; instead it is every interrupt that is not a system
> call?
>
> It also does not follow the lines of "software caused interrupt" vs.
> the rest.
>
>> 4. I'd like to add following types for powerpc.
>>
>> 	PERF_BR_COND_CALL	/* Conditional call */
>> 	PERF_BR_COND_RET	/* Condition return */
> Almost all PowerPC branches have a "conditional" version (only "syscall"
> and "sysret/iret" do not -- and those last two are the same, just like
> PERF_BR_INT seems to be the same as PERF_BR_SYSCALL).
>
> So how should those PERF_BR_* be used?  It cannot be used in an
> architecture-neutral interface the way you define it now.
>
>
> Segher