On Thu, 22 Aug 2013, Robert Richter wrote: > From: Robert Richter <robert.rich...@linaro.org> > > Implementing ioctl functions to control persistent events. There are > functions to detach or attach an event to or from a process. The > PERF_EVENT_IOC_DETACH ioctl call makes an event persistent. After > closing the event's fd it runs then in the background of the system > without the need of a controlling process. The perf_event_open() > syscall can be used to reopen the event by any process. The > PERF_EVENT_IOC_ATTACH ioctl attaches the event again so that it is > removed after closing the event's fd.
> PERF_EVENT_IOC_ATTACH (Since Linux 3.xx) > PERF_EVENT_IOC_DETACH (Since Linux 3.xx) I think these aren't very good names for the ioctls. Maybe something like PERF_EVENT_IOC_MAKE_PERSISTENT PERF_EVENT_IOC_UNPERSIST I know that last one's not a real word but I can't think of what the proper term would be. Maybe PERF_EVENT_IOC_RELEASE_PERSISTENT PERF_EVENT_IOC_RECLAIM_PERSISTENT > This is for Linux man-pages: Thanks, though you're missing out by not learning all about troff formatting. > type ... > > PERF_TYPE_PERSISTENT (Since Linux 3.xx) > > This indicates a persistent event. There is a unique > identifier for each persistent event that needs to be > specified in the event's attribute config field. > Persistent events are listed under: > > /sys/bus/event_source/devices/persistent/ Wait, so the first time you create a persistent event you do *not* set type PERF_TYPE_PERSISTENT? You only do that if you're "attaching" to an exisiting event? You might want to clarify that. > persistent: (Since Linux 3.xx) > > Put event into persistent state after opening. After closing > the event's fd the event is persistent in the system and > continues to run. will there be some sort of tool that will let you kill runaway persistent events? Or will you have to manually perf_event_open() / iotcl() them by hand somehow? > PERF_EVENT_IOC_DETACH (Since Linux 3.xx) > > Detach the event specified by the file descriptor from the > process and make it persistent in the system. After > closing the fd the event will continue to run. An unique > identifier for the persistent event is returned or an > error otherwise. The following allows to connect to the > event again: You might want to re-order things so it's clear you get the unique ID at ioctl time and not after the close happens. > PERF_EVENT_IOC_ATTACH (Since Linux 3.xx) > > Attach the event specified by the file descriptor to the > current process. The event is no longer persistent in the > system and will be removed after all users disconnected > from the event. Thus, if there are no other users the > event will be closed too after closing its file > descriptor, the event then no longer exists. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
