linux-kernel - Re: [PATCH 7/7] perf tools: Refine perf_mmap__read

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Date:   Tue, 6 Mar 2018 08:29:03 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        namhyung@...nel.org, wangnan0@...wei.com, ak@...ux.intel.com
Subject: Re: [PATCH 7/7] perf tools: Refine perf_mmap__read_init



On 3/5/2018 5:25 PM, Jiri Olsa wrote:
> On Mon, Mar 05, 2018 at 02:10:59PM -0500, kan.liang@...ux.intel.com wrote:
> 
> SNIP
> 
>> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
>> index e3921ed..403c5e6 100644
>> --- a/tools/perf/util/mmap.c
>> +++ b/tools/perf/util/mmap.c
>> @@ -235,16 +235,13 @@ static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u6
>>   /*
>>    * Report the start and end of the available data in ringbuffer
>>    */
>> -int perf_mmap__read_init(struct perf_mmap *md, bool overwrite,
>> -			 u64 *startp, u64 *endp)
>> +int perf_mmap__read_init(struct perf_mmap *md, bool overwrite)
>>   {
>>   	u64 head = perf_mmap__read_head(md);
>>   	u64 old = md->prev;
>>   	unsigned char *data = md->base + page_size;
>>   	unsigned long size;
>>   
>> -	*startp = overwrite ? head : old;
>> -	*endp = overwrite ? old : head;
>>   	md->overwrite = overwrite;
> 
> hum, can't we set 'overwrite' at the moment we create struct perf_mmap?
> 
> it's not changing during the mmap's lifetime.. maybe we could do it in
> perf_evlist__alloc_mmap function

Yes, we know that the __alloc_mmap() is for mmap or overwrite_mmap.
I think we can set the 'overwrite' there.
I will do the change in V2.

Thanks,
Kan

> 
> really nice cleanup!
> 
> thanks,
> jirka
>