On Thu, Aug 22, 2019 at 07:54:16AM +0000, Song Liu wrote: > Hi Peter, > > > On Aug 22, 2019, at 12:47 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > On Wed, Aug 21, 2019 at 06:43:49PM +0000, Yonghong Song wrote: > >> On 8/21/19 11:31 AM, Peter Zijlstra wrote: > > > >>> So extending PERF_RECORD_LOST doesn't work. But PERF_FORMAT_LOST might > >>> still work fine; but you get to implement it for all software events. > >> > >> Could you give more specifics about PERF_FORMAT_LOST? Googling > >> "PERF_FORMAT_LOST" only yields two emails which we are discussing here :-( > > > > Look at what the other PERF_FORMAT_ flags do? Basically it is adding a > > field to the read(2) output. > > Do we need to implement PERF_FORMAT_LOST for all software events? If user > space asks for PERF_FORMAT_LOST for events that do not support it, can we > just fail sys_perf_event_open()? It really shouldn't be hard; and I'm failing to see why kprobes are special.
