linux-kernel - Re: [PATCH v13 10/16] perf record: Introduce compressor at mmap buffer object

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Date:   Tue, 1 Feb 2022 11:08:49 +0300
From:   "Bayduraev, Alexey V" <alexey.v.bayduraev@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Antonov <alexander.antonov@...ux.intel.com>,
        Alexei Budankov <abudankov@...wei.com>,
        Riccardo Mancini <rickyman7@...il.com>
Subject: Re: [PATCH v13 10/16] perf record: Introduce compressor at mmap
 buffer object

On 01.02.2022 0:56, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jan 17, 2022 at 09:34:30PM +0300, Alexey Bayduraev escreveu:
>> Introduce compressor object into mmap object so it could be used to
>> pack the data stream from the corresponding kernel data buffer.
>> Initialize and make use of the introduced per mmap compressor.

SNIP

>> --- a/tools/perf/util/mmap.c
>> +++ b/tools/perf/util/mmap.c
>> @@ -230,6 +230,10 @@ void mmap__munmap(struct mmap *map)
>>  {
>>  	bitmap_free(map->affinity_mask.bits);
>>  
>> +#ifndef PYTHON_PERF
>> +	zstd_fini(&map->zstd_data);
>> +#endif
>> +
> 
> Exposing this build detail in the main source code seems ugly, casual
> readers will scratch their heads trying to figure this out, so either
> we should have this behind some macro that hides these deps on a header
> file or add a comment stating why this is needed.

This is quick fix for the fact that the perf.so library for Python is not
compiled with -lzstd, but it includes mmap.c. Probably adding stub macro
to mmap.h would be better.

Regards,
Alexey

> 	
> 
>>  	perf_mmap__aio_munmap(map);
>>  	if (map->data != NULL) {
>>  		munmap(map->data, mmap__mmap_len(map));
>> @@ -292,6 +296,12 @@ int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, struct perf_cpu
>>  	map->core.flush = mp->flush;
>>  
>>  	map->comp_level = mp->comp_level;
>> +#ifndef PYTHON_PERF
>> +	if (zstd_init(&map->zstd_data, map->comp_level)) {
>> +		pr_debug2("failed to init mmap commpressor, error %d\n", errno);
>> +		return -1;
>> +	}
>> +#endif
>>  
>>  	if (map->comp_level && !perf_mmap__aio_enabled(map)) {
>>  		map->data = mmap(NULL, mmap__mmap_len(map), PROT_READ|PROT_WRITE,
>> diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
>> index 62f38d7977bb..cd8b0777473b 100644
>> --- a/tools/perf/util/mmap.h
>> +++ b/tools/perf/util/mmap.h
>> @@ -15,6 +15,7 @@
>>  #endif
>>  #include "auxtrace.h"
>>  #include "event.h"
>> +#include "util/compress.h"
>>  
>>  struct aiocb;
>>  
>> @@ -46,6 +47,7 @@ struct mmap {
>>  	void		*data;
>>  	int		comp_level;
>>  	struct perf_data_file *file;
>> +	struct zstd_data      zstd_data;
>>  };
>>  
>>  struct mmap_params {
>> -- 
>> 2.19.0
>