Em Wed, Aug 21, 2019 at 06:43:49PM +0000, Yonghong Song escreveu: > On 8/21/19 11:31 AM, Peter Zijlstra wrote: > > On Wed, Aug 21, 2019 at 04:54:47PM +0000, Yonghong Song wrote: > >> A lot of bpf-based tracing programs uses maps to communicate and > >> do not allocate ring buffer at all. > > > > 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 :-( Perhaps he's talking about using read(perf_event_fd, ...) after having set it up with perf_event_attr.read_format with the-to-be-implemented PERF_FORMAT_LOST bit? Look at perf_read() and perf_read_one() in kernel/events/core.c. - Arnaldo
