2018-06-19 19:33 GMT+03:00 Steven Rostedt <rostedt@xxxxxxxxxxx>: > On Tue, 19 Jun 2018 19:23:04 +0300 > "Matwey V. Kornilov" <matwey@xxxxxxxxxx> wrote: > >> Hi Steven, >> >> Thank you for valuable comments. >> >> This is for measuring performance of URB completion callback inside PWC driver. >> What do you think about moving events to __usb_hcd_giveback_urb() in >> order to make this more generic? Like the following: >> >> local_irq_save(flags); >> // trace urb complete enter >> urb->complete(urb); >> // trace urb complete exit >> local_irq_restore(flags); >> >> > > If that can work for you, I'm fine with that. Trace events may be > cheap, but they do come with some cost. I'd like to have all trace > events be as valuable as possible, and limit the "special case" ones. What is the cost for events? I suppose one conditional check when trace is disabled? There is already similar debugging stuff related to usbmon in __usb_hcd_giveback_urb(), so I don't think that another conditional check will hurt performance dramatically there. When discussing second patch in this series I see that the issue that it is intended to resolve may be common to other USB media drivers. > > -- Steve > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119234, Moscow, Universitetsky pr-k 13, +7 (495) 9392382
