Extract event reader from perf_evlist__mmap_read() to perf__mmap_read().
Future commit will feed it with manually computed 'head' and 'old'
pointers.
Signed-off-by: NWang Nan <wangnan0@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1461723563-67451-2-git-send-email-wangnan0@huawei.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>