On Fri, Jan 02, 2015 at 08:31:33AM -0700, David Ahern wrote: > On 1/1/15 7:59 PM, Shaohua Li wrote: > >I'm wondering how we could use the perf to implament a clock_gettime. > >reading the perf fd or using ioctl is slow so reading the mmap > >ringbuffer is the only option. But as far as I know the ringbuffer has > >data only when an event is generated. Between two events, there is > >nothing we can read from the ringbuffer. Then how can application get > >time info in the interval? > > Are you wanting to read perf_clock from userspace?
Yep, in some sort of form. Basically I want to read the time a task runs. Peter suggests we can read the activation time of a perf event. But I don't want to use any system call, as it's slow and likes clock_gettime. Thanks, Shaohua -- 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/
