On Wed, Oct 21, 2015 at 11:06 AM, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, Oct 21, 2015 at 05:53:13PM +0200, Tomeu Vizoso wrote: >> On 21 October 2015 at 17:14, Greg Kroah-Hartman >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Wed, Oct 21, 2015 at 04:35:58PM +0200, Tomeu Vizoso wrote: >> >> On 21 October 2015 at 05:39, Greg Kroah-Hartman >> >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> >> > On Tue, Oct 20, 2015 at 06:17:39PM +0200, Tomeu Vizoso wrote: >> >> >> On 20 October 2015 at 16:05, Greg Kroah-Hartman >> >> >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> >> >> > On Tue, Oct 20, 2015 at 09:40:48AM +0200, Tomeu Vizoso wrote: >> >> >> >> On 19 October 2015 at 17:19, Greg Kroah-Hartman >> >> >> >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> >> >> >> > On Mon, Oct 19, 2015 at 05:13:22PM +0200, Tomeu Vizoso wrote: >> >> >> >> >> To smooth the transition to late probes, make disabled the default for >> >> >> >> >> DELAY_DEVICE_PROBES and let individual SoCs enable the option as they >> >> >> >> >> get fixed. >> >> >> >> >> >> >> >> >> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> >> >> >> >> >> Link: https://lkml.kernel.org/g/20151016181129.GA1764@xxxxxxxxxxxx >> >> >> >> >> >> >> >> >> >> --- >> >> >> >> >> >> >> >> >> >> Hi Rob, >> >> >> >> >> >> >> >> >> >> I'm sending this in case you think it would be best to leave the >> >> >> >> >> on-demand probe series in -next for now but have late probes disabled to >> >> >> >> >> avoid hassle to some people. >> >> >> >> > >> >> >> >> > I would like Rob to just drop this series please, I don't agree with it >> >> >> >> > at all at the moment. >> >> >> >> >> >> >> >> Hi Greg, >> >> >> >> >> >> >> >> is it the case that you are satisfied with deferred probes as a way of >> >> >> >> ordering device probing and that I should look at how to solve my >> >> >> >> problem by improving it? >> >> >> > >> >> >> > Yes, especially given that you have said this does not speed up your >> >> >> > boot times, which I thought was your main goal here :( >> >> >> >> >> >> Sorry if I'm repeating myself too often, but I have two goals: change >> >> >> the probing order to not send deferred probes to the back of the queue >> >> >> (getting the display up as fast as possible), and making easier to >> >> >> understand the boot process on embedded platforms. >> >> >> >> >> >> The concrete issue that would be fixed by achieving the first goal was >> >> >> explained in this email from last year: >> >> >> >> >> >> http://lists.freedesktop.org/archives/dri-devel/2014-August/066527.html >> >> >> >> >> >> Because of that, ChromeOS had to use their own bindings for the panel >> >> >> node so that the panel probe wouldn't be deferred, introducing a >> >> >> sizable delta that is a barrier to rebasing on newer mainline releases >> >> >> and for vendors to upstream their HW adaptation for chrome devices. >> >> > >> >> > 1.5 second delay is crazy (again, my laptop boots to X in less time than >> >> > that), >> >> >> >> 1.5 seconds isn't crazy at all for the kernel to initialize all the >> >> devices in an embedded board. That's the current state of affairs >> >> today. >> > >> > Then someone needs to fix that, that really is crazy. What takes so >> > long here? Why aren't you using async probing to do things in parallel >> > when you need to sleep in device probe (I'm hoping you are sleeping in >> > device probe, otherwise that's really broken)? >> >> I'm a bit surprised now. During all the time that I have been pushing >> this forward I have been regularly testing on more than a dozen boards >> with different socs and 1.5 seconds to probe all the devices isn't >> that much. This is basically due to having to wait for the hardware a >> bit here and there, and to the sheer number of devices involved. >> >> Of course people have been looking at speeding up boot on ARM devices >> for years now and this is what we have come with up to now. >> >> > Have you used the tools we have to find where the time is being spent? >> >> Have to recognize that my starting point has been that probe order was >> the cause of the problem and haven't profiled the whole boot process, >> but I don't see how probe ordering would become irrelevant unless we >> got total probing time down to 200ms. And that would give us a >> fabulously fast boot, which I don't think is as realistic as you seem >> to believe. > > So you aren't using the tools that we have today that were created years > ago, to help to reduce boot time problems like this and instead work on > changing the driver core to try to guess at what the real issue is here? > > Come on, until you really know where you are taking so long, how can you > know what you need to fix? I strongly recommend doing that here first, > that's why those tools were written in the first place. For something everyone is or should be doing for years, there is surprisingly zero information I can find. It is perf timechart you are talking about, right? Everything I find on it is all after userspace starts. I know perf has command line options, but I never could get it to do what I wanted (which was dumping events up until a boot hang). Still, the 1.5 sec doesn't surprise me either. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
