Em Fri, May 20, 2016 at 11:31:44PM +0800, Wangnan (F) escreveu: > > > On 2016/5/13 21:08, Arnaldo Carvalho de Melo wrote: > > Em Fri, May 13, 2016 at 07:56:06AM +0000, Wang Nan escreveu: > > > Detect avalibility of write_backward and save the result into > > > record_opts. With write_backward the start pointer of a ring > > > buffer mapped read only can be found reliably. > > We have perf_missing_features for that, please try to use it. > > I'll try it, but write_backward can't fallback, if kernel doesn't > support it, I think we'd better throw an error earlier. Using > perf_missing_features we get error during opening the event, so if we want > to fail earlier we still need API probing.
Conceptually 'perf_missing_features' shouldn't be strictly tied to fallbacking, its just a way to mark what perf features are missing in the current kernel, that info may be used for fallbacking, or for any other purpose. - Arnaldo
