linux-kernel - Re: [PATCH] perf util: Join four conditions in two in perf_evlist__create

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Date:	Wed, 27 Nov 2013 19:36:31 -0500
From:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
CC:	linux-kernel@...r.kernel.org, dsahern@...il.com, jolsa@...hat.com,
	namhyung@...nel.org, acme@...stprotocols.net, mingo@...hat.com
Subject: Re: [PATCH] perf util: Join four conditions in two in perf_evlist__create_maps().

On 11/27/2013 05:49 AM, Adrian Hunter wrote:
> On 28/11/13 00:52, Dongsheng Yang wrote:
>> On 11/27/2013 04:43 AM, Adrian Hunter wrote:
>>> On 28/11/13 00:23, Dongsheng Yang wrote:
>>>> There are four condition branchs in perf_evlist__create_maps, but they
>>>> only do two kinds of thing. 1st and 4th call cpu_map__new(), and the others
>>>> call cpu_map__dummy_new(). This patch joins them in two branchs, decreasing
>>>> the number of branch and removing some duplicated code.
>>> That code has changed again.  See:
>>>
>>>      http://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/log/?h=perf/core
>>>
>>>
>> Hi Adrian!
>>      Thanx for your reminding. Yes, a more checking is added into the 1st
>> branch.
>> And I think we still can join them in two conditions.
>>
>> Do you think this idea is ok to you? If so, I will update my patch base on
>> the latest code.
> Personally I like code that is easy to read, and I don't think
> combining the conditions does that.  But you could set a bool
> and use that to decide what to call.
>

How about add a function in target.c named 
perf_target__uses_dummy_map(), and this
function take over the all checking to decide which to call. Then we can 
use it here like:

if (perf_target__uses_dummy_map(target)):
     evlist->cpus = cpu_map__dummy_new();
else:
     evlist->cpus = cpu_map__new(target->cpu_list);
>> Yang
>>>> Signed-off-by: Dongsheng Yang <yangds.fnst@...fujitsu.com>
>>>> ---
>>>>    tools/perf/util/evlist.c | 8 +++-----
>>>>    1 file changed, 3 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>>>> index bbc746a..2258eb4 100644
>>>> --- a/tools/perf/util/evlist.c
>>>> +++ b/tools/perf/util/evlist.c
>>>> @@ -819,11 +819,9 @@ int perf_evlist__create_maps(struct perf_evlist
>>>> *evlist, struct target *target)
>>>>        if (evlist->threads == NULL)
>>>>            return -1;
>>>>    -    if (target->force_per_cpu)
>>>> -        evlist->cpus = cpu_map__new(target->cpu_list);
>>>> -    else if (target__has_task(target))
>>>> -        evlist->cpus = cpu_map__dummy_new();
>>>> -    else if (!target__has_cpu(target) && !target->uses_mmap)
>>>> +    if (!target->force_per_cpu &&
>>>> +        (target__has_task(target) ||
>>>> +         (!target__has_cpu(target) && !target->uses_mmap)))
>>>>            evlist->cpus = cpu_map__dummy_new();
>>>>        else
>>>>            evlist->cpus = cpu_map__new(target->cpu_list);
>>>>
>>
>>
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