linux-kernel - Re: [PATCH v9 2/7] perf/x86/intel: Record branch type

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Date:   Mon, 17 Jul 2017 10:11:12 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.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 v9 2/7] perf/x86/intel: Record branch type

On Mon, Jul 17, 2017 at 07:06:38PM +0800, Jin Yao wrote:

SNIP

> +#define X86_BR_TYPE_MAP_MAX	16
> +
> +static int
> +common_branch_type(int type)
> +{
> +	int i;
> +	const int branch_map[X86_BR_TYPE_MAP_MAX] = {
> +		PERF_BR_CALL,		/* X86_BR_CALL */
> +		PERF_BR_RET,		/* X86_BR_RET */
> +		PERF_BR_SYSCALL,	/* X86_BR_SYSCALL */
> +		PERF_BR_SYSRET,		/* X86_BR_SYSRET */
> +		PERF_BR_UNKNOWN,	/* X86_BR_INT */
> +		PERF_BR_UNKNOWN,	/* X86_BR_IRET */
> +		PERF_BR_COND,		/* X86_BR_JCC */
> +		PERF_BR_UNCOND,		/* X86_BR_JMP */
> +		PERF_BR_UNKNOWN,	/* X86_BR_IRQ */
> +		PERF_BR_IND_CALL,	/* X86_BR_IND_CALL */
> +		PERF_BR_UNKNOWN,	/* X86_BR_ABORT */
> +		PERF_BR_UNKNOWN,	/* X86_BR_IN_TX */
> +		PERF_BR_UNKNOWN,	/* X86_BR_NO_TX */
> +		PERF_BR_CALL,		/* X86_BR_ZERO_CALL */
> +		PERF_BR_UNKNOWN,	/* X86_BR_CALL_STACK */
> +		PERF_BR_IND,		/* X86_BR_IND_JMP */
> +	};

should the branch_map array be static? having it on stack makes
the compiler to create it every time we call the function

jirka

> +
> +	type >>= 2; /* skip X86_BR_USER and X86_BR_KERNEL */
> +
> +	if (type) {
> +		i = __ffs(type);
> +		if (i < X86_BR_TYPE_MAP_MAX)
> +			return branch_map[i];
> +	}
> +
> +	return PERF_BR_UNKNOWN;
> +}
> +
>  /*
>   * implement actual branch filter based on user demand.
>   * Hardware may not exactly satisfy that request, thus
> @@ -942,7 +987,8 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc)
>  	bool compress = false;
>  
>  	/* if sampling all branches, then nothing to filter */
> -	if ((br_sel & X86_BR_ALL) == X86_BR_ALL)
> +	if (((br_sel & X86_BR_ALL) == X86_BR_ALL) &&
> +	    ((br_sel & X86_BR_TYPE_SAVE) != X86_BR_TYPE_SAVE))
>  		return;
>  
>  	for (i = 0; i < cpuc->lbr_stack.nr; i++) {
> @@ -963,6 +1009,9 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc)
>  			cpuc->lbr_entries[i].from = 0;
>  			compress = true;
>  		}
> +
> +		if ((br_sel & X86_BR_TYPE_SAVE) == X86_BR_TYPE_SAVE)
> +			cpuc->lbr_entries[i].type = common_branch_type(type);
>  	}
>  
>  	if (!compress)
> -- 
> 2.7.4
>