On Saturday, May 19, 2012, Sameer Nanda wrote: > On Fri, May 18, 2012 at 4:01 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, May 18, 2012 at 03:17:32PM -0700, Sameer Nanda wrote: > >> On Fri, May 18, 2012 at 2:46 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > >> > On Friday, May 18, 2012, Sameer Nanda wrote: > >> >> On Fri, May 18, 2012 at 2:19 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > >> >> > On Fri, 2012-05-18 at 13:58 -0700, Sameer Nanda wrote: > >> >> >> On Fri, May 18, 2012 at 12:14 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > >> >> >> > On Fri, 2012-05-18 at 11:57 -0700, Sameer Nanda wrote: > >> >> >> > > >> >> >> >> AFAICT, they are used for something completely different -- help solve > >> >> >> >> suspend/resume issues by saving a hash in the RTC of the last device > >> >> >> >> that suspended/resumed. They don't use the perf tracing mechanism at > >> >> >> >> all. > >> >> >> >> > >> >> >> > > >> >> >> > Also note that all tracepoints have timestamps attached to them. You do > >> >> >> > not need to add deltas. Do that in the userspace tools that read the > >> >> >> > timestamps and events. This way you can have one DECLARE_EVENT_CLASS and > >> >> >> > three DEFINE_EVENTs. This will save space. > >> >> >> > >> >> >> Agreed on the space savings. However, with the time_delta in the > >> >> >> trace message itself, a one line shell script [1] that sorts on the > >> >> >> time_delta field is sufficient to quickly spot the devices that take a > >> >> >> long time to resume. Without the time_delta field, the user tool is > >> >> >> more complex since it needs to first match up the device_resume_in, > >> >> >> device_resume_waited and device_resume_out traces and then calculate > >> >> >> time deltas. > >> >> >> > >> >> >> Seems like a worthwhile trade-off to me but I can take out the > >> >> >> time_delta if the general consensus is otherwise. > >> >> > > >> >> > Just note that every TRACE_EVENT() adds around 5k or more code. Every > >> >> > DEFINE_EVENT adds just about 300 bytes. > >> >> > >> >> Ok, let me respin the patch. I am thinking of adding time_delta to > >> >> all three traces. That way we should get the space saving while still > >> >> allowing quick spotting of devices that take long time to resume. > >> > > >> > Well, what's wrong with the code in drivers/base/power/main.c that > >> > is activated by adding initcall_debug to the kernel command line? > >> > >> Mostly that I hadn't looked closely at initcall_debug before writing my patch :) > >> > >> Now that I have taken a look at it, the main issue is that the kernel > >> command line needs to be modified to activate it. We cannot do this > >> for our automated regression suites since the kernel command line is > >> protected on Chrome OS systems. > > > > You are kidding, right? You have control over your test systems, don't > > bloat everyone's kernel by 5k just because your infrastructure is > > somehow something that you feel you can't change. > > Fair enough. But having to modify the kernel command line to do this > is clunky. How about exposing the ability to turn on these > initcall_debug prints through a knob under /sys/power? This might work, but first you'd need to make them depend on something different from initcall_debug (and make that thing in turn be set if initcall_debug is put into the kernel command line). Then, you could export the new variable. Greg, does that make sense to you? Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
