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

Alexey Budankov
2018-10-08T12:24:37Z

Hi,

On 08.10.2018 13:52, Jiri Olsa wrote:
> On Mon, Oct 08, 2018 at 09:17:11AM +0300, Alexey Budankov wrote:
<SNIP>
>> +#ifdef HAVE_AIO_SUPPORT
>> + off = lseek(trace_fd, 0, SEEK_CUR);
>> +#endif
>
> I'm still little puzzled why we need to do this,
> when the aio write takes the offset value, but

pwrite() syscall [1] which is the base for aio_write() doesn't
advance file pos value so it requires to be calculated and
updated by callers of aio_write() API.

> please provide some aio_.. function for this

Accepted.

>
>
>> 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
>> }
>>
>> if (map->auxtrace_mmap.base && !rec->opts.auxtrace_snapshot_mode &&
>> @@ -547,7 +694,9 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
>> goto out;
>> }
>> }
>> -
>> +#ifdef HAVE_AIO_SUPPORT
>> + lseek(trace_fd, off, SEEK_SET);
>> +#endif
>
> ditto

Accepted.

Thanks,
Alexey

>
> thanks,
> jirka
>

[1] http://man7.org/linux/man-pages/man2/pread.2.html