linux-kernel - Re: [PATCH v11 2/3]: perf record: enable asynchronous trace writing

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Date:   Mon, 8 Oct 2018 15:15:05 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 2/3]: perf record: enable asynchronous trace writing

Hi,

On 08.10.2018 13:57, Jiri Olsa wrote:
> On Mon, Oct 08, 2018 at 09:17:11AM +0300, Alexey Budankov wrote:
> 
> SNIP
> 
>>  static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evlist,
>>  				    bool overwrite)
>>  {
>> @@ -520,7 +644,10 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
>>  	int i;
>>  	int rc = 0;
>>  	struct perf_mmap *maps;
>> -
>> +#ifdef HAVE_AIO_SUPPORT
>> +	int trace_fd = rec->data.file.fd;
>> +	off_t off;
>> +#endif
>>  	if (!evlist)
>>  		return 0;
>>  
>> @@ -531,14 +658,34 @@ 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;
>>  
>> +#ifdef HAVE_AIO_SUPPORT
>> +	off = lseek(trace_fd, 0, SEEK_CUR);
>> +#endif
>>  	for (i = 0; i < evlist->nr_mmaps; i++) {
>>  		struct perf_mmap *map = &maps[i];
>>  
>>  		if (map->base) {
>> -			if (perf_mmap__push(map, rec, record__pushfn) != 0) {
>> -				rc = -1;
>> -				goto out;
>> +#ifdef HAVE_AIO_SUPPORT
>> +			if (!rec->opts.nr_cblocks) {
>> +#endif
>> +				if (perf_mmap__push(map, rec, record__pushfn) != 0) {
>> +					rc = -1;
>> +					goto out;
>> +				}
>> +#ifdef HAVE_AIO_SUPPORT
>> +			} else {
>> +				/*
>> +				 * Call record__aio_sync() to wait till map->data buffer
>> +				 * becomes available after previous aio write request.
>> +				 */
>> +				record__aio_sync(map);
>> +				if (perf_mmap__aio_push(map, rec, record__aio_pushfn, &off) != 0) {
>> +					lseek(trace_fd, off, SEEK_SET);
>> +					rc = -1;
>> +					goto out;
>> +				}
>>  			}
>> +#endif
> 
> I really don't like this.. let's have some aio_... function with its
> dummy counterpart to be called in here.. and again.. if we realyl must
> have this compiled optionaly, which I'm not convinced of

Accepted.

Thanks,
Alexey

> 
> jirka
>