linux-kernel - Re: [PATCH V2] tipc: Use bsearch library function

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Date:   Sat, 16 Sep 2017 18:10:57 +0800
From:   Ying Xue <ying.xue@...driver.com>
To:     Joe Perches <joe@...ches.com>, Thomas Meyer <thomas@...3r.de>,
        <jon.maloy@...csson.com>, <netdev@...r.kernel.org>,
        <tipc-discussion@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <davem@...emloft.net>
Subject: Re: [PATCH V2] tipc: Use bsearch library function

On 09/16/2017 05:58 PM, Joe Perches wrote:
> On Sat, 2017-09-16 at 17:36 +0800, Ying Xue wrote:
>> On 09/16/2017 05:26 PM, Joe Perches wrote:
>>> On Sat, 2017-09-16 at 17:02 +0800, Ying Xue wrote:
>>>> On 09/16/2017 03:50 PM, Thomas Meyer wrote:
>>>>> Use common library function rather than explicitly coding
>>>>> some variant of it yourself.
>>>>>
>>>>> Signed-off-by: Thomas Meyer <thomas@...3r.de>
>>>>
>>>> Acked-by: Ying Xue <ying.xue@...driver.com>
>>>
>>> Are you sure you want to do this?
>>>
>>> Note the comment above nameseq_find_subseq
>>>
>>>  * Very time-critical, so binary searches through sub-sequence array.
>>>
>>> What impact does this change have on performance?
>>
>> Sorry, I couldn't see any essential difference between this new
>> implementation and the original one except that the former tries to use
>> the library function - bsearch() to replace the original binary search
>> algorithm implemented in TIPC itself. Therefore, I don't think the
>> change will have a big impact on performance.
>>
>> If I miss something, please let me know.
> 
> Comparison via a function pointer in bsearch is slower
> than direct code without the function call overhead.
> 

Right, but probably we can tolerate the slight sacrifice here.

>