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

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Date:   Thu, 21 Feb 2019 14:18:08 +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 21.02.2019 12:43, Jiri Olsa wrote:
> On Wed, Feb 20, 2019 at 05:53:17PM +0300, Alexey Budankov wrote:
>>
>> On 12.02.2019 16:08, Jiri Olsa wrote:
>>> On Mon, Feb 11, 2019 at 11:23:40PM +0300, Alexey Budankov wrote:
>>>
>>> SNIP
>>>
>>>> @@ -774,6 +775,8 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
>>>>  	struct perf_mmap *maps;
>>>>  	int trace_fd = rec->data.file.fd;
>>>>  	off_t off;
>>>> +	struct perf_session *session = rec->session;
>>>> +	perf_mmap__compress_fn_t compress_fn;
>>>>  
>>>>  	if (!evlist)
>>>>  		return 0;
>>>> @@ -785,6 +788,9 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
>>>>  	if (overwrite && evlist->bkw_mmap_state != BKW_MMAP_DATA_PENDING)
>>>>  		return 0;
>>>>  
>>>> +	compress_fn = (record__comp_enabled(rec) ?
>>>> +		perf_session__zstd_compress : perf_session__zstd_copy);
>>>> +
>>>
>>> I don't follow what's the perf_session__zstd_copy function for..?
>>
>> It bridges AIO without compression case.
> 
> so current state then.. why do we need new function for that?

This copy() function has the same signature as compress() 
so it can be used as the replacement in the _pack() call 
instead of memcpy() with different signature.

Thanks,
Alexey

> 
> jirka