linux-kernel - Re: [PATCH v2 3/4] perf record: enable runtime trace compression

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Date:   Wed, 20 Feb 2019 18:03:44 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] perf record: enable runtime trace compression


On 12.02.2019 16:09, Jiri Olsa wrote:
> On Mon, Feb 11, 2019 at 11:23:40PM +0300, Alexey Budankov wrote:
> 
> SNIP
> 
>> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
>> index 239e9a13c2b7..980784b77fe2 100644
>> --- a/tools/perf/util/mmap.c
>> +++ b/tools/perf/util/mmap.c
>> @@ -156,6 +156,86 @@ void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __mayb
>>  {
>>  }
>>  
>> +static ssize_t perf_mmap__capture(struct perf_mmap *md, int idx,
>> +			perf_mmap__compress_fn_t compress, void *where)
> 
> what's the point of casting perf_session* to void* ? all the way down to
> the compression, where you cast it back?
> 
> SNIP
> 
>> +int perf_session__zstd_fini(struct perf_session *session)
>> +{
>> +	if (session->zstd_cstream) {
>> +		ZSTD_freeCStream(session->zstd_cstream);
>> +		session->zstd_cstream = NULL;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +size_t perf_session__zstd_compress(void *to,  void *dst, size_t dst_size,
>> +				   void *src, size_t src_size)
>> +{
>> +	struct perf_session *session = to;
> 
> in here... it could be just struct perf_session* no?

As far as it is a pointer. Casting a pointer to void* 
and back is harmless. Well, let's clean that up.

Thanks,
Alexey

> 
> jirka
>