On Fri, 21 Oct 2016, Wang Nan wrote: > context_switch : 1, /* context switch data */ > - > - __reserved_1 : 37; > + write_backward : 1, /* Write ring buffer from end to beginning */ > + __reserved_1 : 36; This removes a blank line, not sure if intentional or not. > +.IR "write_backward" " (since Linux 4.6)" It didn't committed until Linux 4.7 from what I can tell? > +This makes the resuling event use a backward ring-buffer, which resulting > +writes samples from the end of the ring-buffer. > + > +It is not allowed to connect events with backward and forward > +ring-buffer settings together using > +.B PERF_EVENT_IOC_SET_OUTPUT. > + > +Backward ring-buffer is useful when the ring-buffer is overwritable > +(created by readonly > +.BR mmap (2) > +). A ring buffer is over-writable when it is mmapped readonly? Is this a hard requirement? Can you set the read-backwards bit if not mapped readonly? Otherwise the documentation seems reasonable. Reviewed-by: Vince Weaver <vincent.weaver@xxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
