linux-imx

perf record: Enable asynchronous trace writing

The trace file offset is read once before mmaps iterating loop and
written back after all performance data is enqueued for aio writing.

The trace file offset is incremented linearly after every successful aio
write operation.

record__aio_sync() blocks till completion of the started AIO operation
and then proceeds.

record__aio_mmap_read_sync() implements a barrier for all incomplete
aio write requests.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/ce2d45e9-d236-871c-7c8f-1bed2d37e8ac@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>