linux-kernel - Re: [PATCH v4 4/7] perf diff: Use hists to manage basic blocks per symbol

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Date:   Mon, 24 Jun 2019 22:49:25 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v4 4/7] perf diff: Use hists to manage basic blocks per
 symbol

On 6/24/2019 3:57 PM, Jiri Olsa wrote:
> On Thu, Jun 20, 2019 at 10:36:39PM +0800, Jin Yao wrote:
> 
> SNIP
> 
>> +
>> +static void *block_entry_zalloc(size_t size)
>> +{
>> +	return zalloc(size + sizeof(struct hist_entry));
>> +}
>> +
>> +static void block_entry_free(void *he)
>> +{
>> +	struct block_info *bi = ((struct hist_entry *)he)->block_info;
>> +
>> +	block_info__put(bi);
>> +	free(he);
>> +}
>> +
>> +struct hist_entry_ops block_entry_ops = {
>> +	.new    = block_entry_zalloc,
>> +	.free   = block_entry_free,
>> +};
> 
> hum, so there's already block_hist_ops moving that stuff into 'struct block_hist',
> which is great, but why don't we have 'struct block_entry' in here? that would
> keep the 'struct block_info'
> 
> thanks,
> jirka
> 

Hi Jiri,

If I define 'struct block_entry' as following and cast 'he' to 'struct 
block_entry' in some places, such as in block_cmp(), we can get the 
'struct block_entry'.

struct block_entry {
	struct block_info bi;
	struct hist_entry he;
};

But I don't know when I can set the 'bi' of 'struct block_entry'. Before 
or after calling hists__add_entry_xxx()? Before calling 
hists__add_entry_xxx(), we don't know the hist_entry. After calling 
hists__add_entry_xxx(), actually the hist_entry__cmp doesn't work (no bi ).

That's why I create block_info in hist_entry. Maybe I misunderstand what 
your suggested, correct me if I'm wrong.

Thanks
Jin Yao