linux-kernel - Re: [PATCH 2/2] perf tools: Construct LBR call chain

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Date:	Wed, 12 Nov 2014 13:33:43 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	kan.liang@...el.com
Cc:	acme@...nel.org, a.p.zijlstra@...llo.nl, eranian@...gle.com,
	linux-kernel@...r.kernel.org, mingo@...hat.com, paulus@...ba.org,
	ak@...ux.intel.com
Subject: Re: [PATCH 2/2] perf tools: Construct LBR call chain

On Thu, Nov 06, 2014 at 09:58:06AM -0500, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
> 

SNIP

> +	/* LBR call stack */
> +	if (lbr) {
> +		struct branch_stack *lbr_stack = sample->branch_stack;
> +		int lbr_nr = lbr_stack->nr;
> +		int mix_chain_nr;
>  
> -		if (callchain_param.order == ORDER_CALLEE)
> -			j = i;
> -		else
> -			j = chain->nr - i - 1;
> +		for (i = 0; i < chain_nr; i++) {
> +			if (chain->ips[i] == PERF_CONTEXT_USER)
> +				break;
> +		}
>  
> -#ifdef HAVE_SKIP_CALLCHAIN_IDX
> -		if (j == skip_idx)
> -			continue;
> -#endif
> -		ip = chain->ips[j];
> +		/* LBR only affects the user callchain */
> +		if (i == chain_nr) {
> +			lbr = 0;
> +			goto again;
> +		}

'goto again' sounds like u want to try something again,
but you prepare the condition already with lbr = 0,
could you please restruct the code in another way?


SNIP

> +				goto exit;
>  		}
> +	} else {
>  
> -		err = callchain_cursor_append(&callchain_cursor,
> -					      ip, al.map, al.sym);
> -		if (err)
> -			return err;
> -	}
> +		/*
> +		 * Based on DWARF debug information, some architectures skip
> +		 * a callchain entry saved by the kernel.
> +		 */
> +		skip_idx = arch_skip_callchain_idx(thread, chain);
>  
> -	return 0;
> +		for (i = 0; i < chain_nr; i++) {
> +			struct addr_location al;
> +
> +			if (callchain_param.order == ORDER_CALLEE)
> +				j = i;
> +			else
> +				j = chain->nr - i - 1;
> +
> +#ifdef HAVE_SKIP_CALLCHAIN_IDX
> +			if (j == skip_idx)
> +				continue;
> +#endif
> +			ip = chain->ips[j];
> +			err = __thread__resolve_callchain_sample(thread,

Uou factored out the common functionality into __thread__resolve_callchain_sample
function and added your own functionality.. could you please split this into 2
separate patches? (first the new function, then your change)
IMO It'll make the change simple and more obvious.

thanks,
jirka
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