linux-kernel - Re: [PATCH v7 1/7] perf/core: Define the common branch type classification

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Date:   Tue, 11 Jul 2017 14:06:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, mpe@...erman.id.au,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v7 1/7] perf/core: Define the common branch type
 classification

On Tue, Jul 11, 2017 at 11:00:57PM +0800, Jin Yao wrote:
> PERF_BR_NONE            : unknown

I would suggest PERF_BR_UNKNOWN or PERF_BR_MISC, since PERF_BR_NONE
reads like it wasn't a branch at all.

> PERF_BR_COND            ：conditional
> 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 (reserve 5 for future branch types)

What's up with that 5 ? I can't see anything like that in the patch
itself:

> @@ -1024,7 +1048,8 @@ struct perf_branch_entry {
>  		in_tx:1,    /* in transaction */
>  		abort:1,    /* transaction abort */
>  		cycles:16,  /* cycle count to last branch */
> -		reserved:44;
> +		type:4,     /* branch type */
> +		reserved:40;
>  };