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Date: Sun, 20 Dec 2009 00:10:19 +0100 From: "Rafael J. Wysocki" <rjw@...k.pl> To: Dmitry Torokhov <dmitry.torokhov@...il.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Alan Stern <stern@...land.harvard.edu>, Zhang Rui <rui.zhang@...el.com>, LKML <linux-kernel@...r.kernel.org>, ACPI Devel Maling List <linux-acpi@...r.kernel.org>, pm list <linux-pm@...ts.linux-foundation.org> Subject: Re: Async suspend-resume patch w/ completions (was: Re: Async suspend-resume patch w/ rwsems) On Saturday 19 December 2009, Dmitry Torokhov wrote: > On Dec 19, 2009, at 1:33 PM, "Rafael J. Wysocki" <rjw@...k.pl> wrote: > > > On Saturday 19 December 2009, Dmitry Torokhov wrote: > >> On Fri, Dec 18, 2009 at 11:43:29PM +0100, Rafael J. Wysocki wrote: > >>> On Wednesday 16 December 2009, Dmitry Torokhov wrote: > >>>> On Wed, Dec 16, 2009 at 03:11:05AM +0100, Rafael J. Wysocki wrote: > >>>>> On Tuesday 15 December 2009, Linus Torvalds wrote: > >>>>>> > >>>>>> On Tue, 15 Dec 2009, Rafael J. Wysocki wrote: > >>>>>>>> > >>>>>>>> Give a real example that matters. > >>>>>>> > >>>>>>> I'll try. Let -> denote child-parent relationships and assume > >>>>>>> dpm_list looks > >>>>>>> like this: > >>>>>> > >>>>>> No. > >>>>>> > >>>>>> I mean something real - something like > >>>>>> > >>>>>> - if you run on a non-PC with two USB buses behind non-PCI > >>>>>> controllers. > >>>>>> > >>>>>> - device xyz. > >>>>>> > >>>>>>> If this applies to _resume_ only, then I agree, but the > >>>>>>> Arjan's data clearly > >>>>>>> show that serio devices take much more time to suspend than USB. > >>>>>> > >>>>>> I mean in general - something where you actually have hard data > >>>>>> that some > >>>>>> device really needs anythign more than my one-liner, and really > >>>>>> _needs_ > >>>>>> some complex infrastructure. > >>>>>> > >>>>>> Not "let's imagine a case like xyz". > >>>>> > >>>>> As I said I would, I made some measurements. > >>>>> > >>>>> I measured the total time of suspending and resuming devices as > >>>>> shown by the > >>>>> code added by this patch: > >>>>> http://git.kernel.org/?p=linux/kernel/git/rafael/suspend-2.6.git;a=commitdiff_plain;h=c1b8fc0a8bff7707c10f31f3d26bfa88e18ccd94;hp=087dbf5f079f1b55cbd3964c9ce71268473d5b67 > >>>>> on two boxes, HP nx6325 and MSI Wind U100 (hardware-wise they > >>>>> are quite > >>>>> different and the HP was running 64-bit kernel and user space). > >>>>> > >>>>> I took four cases into consideration: > >>>>> (1) synchronous suspend and resume (/sys/power/pm_async = 0) > >>>>> (2) asynchronous suspend and resume as introduced by the async > >>>>> branch at: > >>>>> http://git.kernel.org/?p=linux/kernel/git/rafael/suspend-2.6.git;a=shortlog;h=refs/heads/async > >>>>> (3) asynchronous suspend and resume like in (2), but with your > >>>>> one-liner setting > >>>>> the power.async_suspend flag for PCI bridges on top > >>>>> (4) asynchronous suspend and resume like in (2), but with an > >>>>> extra patch that > >>>>> is appended on top > >>>>> > >>>>> For those tests I set power.async_suspend for all USB devices, > >>>>> all serio input > >>>>> devices, the ACPI battery and the USB PCI controllers (to see > >>>>> the impact of the > >>>>> one-liner, if any). > >>>>> > >>>>> I carried out 5 consecutive suspend-resume cycles (started from > >>>>> under X) on > >>>>> each box in each case, and the raw data are here (all times in > >>>>> milliseconds): > >>>>> http://www.sisk.pl/kernel/data/async-suspend.pdf > >>>>> > >>>>> The summarized data are below (the "big" numbers are averages > >>>>> and the +/- > >>>>> numbers are standard deviations, all in milliseconds): > >>>>> > >>>>> HP nx6325 MSI Wind U100 > >>>>> > >>>>> sync suspend 1482 (+/- 40) 1180 (+/- 24) > >>>>> sync resume 2955 (+/- 2) 3597 (+/- 25) > >>>>> > >>>>> async suspend 1553 (+/- 49) 1177 (+/- 32) > >>>>> async resume 2692 (+/- 326) 3556 (+/- 33) > >>>>> > >>>>> async+one-liner suspend 1600 (+/- 39) 1212 (+/- 41) > >>>>> async+one-liner resume 2692 (+/- 324) 3579 (+/- 24) > >>>>> > >>>>> async+extra suspend 1496 (+/- 37) 1217 (+/- 38) > >>>>> async+extra resume 1859 (+/- 114) 1923 (+/- 35) > >>>>> > >>>>> So, in my opinion, with the above set of "async" devices, it > >>>>> doesn't > >>>>> make sense to do async suspend at all, because the sync suspend > >>>>> is actually > >>>>> the fastest on both machines. > >>>> > >>>> I think the async suspend is not asynchronous enough then - what > >>>> kind of > >>>> time do you get if you simply comment out call to psmouse_reset() > >>>> in > >>>> drivers/input/mouse/psmouse-base.c:psmouse_cleanup()? (Just for > >>>> testing > >>>> purposes only, I don't think we want to do that by default.) > >>> > >>> The problem apparently is that the i8042 suspend/resume is > >>> synchronous. > >>> > >>> Do you think it's safe to mark it as asynchronous? > >>> > >> > >> Umm.. there lie dragons. There is an implicit relationship between > >> i8042 > >> and PNP/ACPI devices representing keyboard and mouse ports, and I > >> am not > >> sure how happy i8042 (and most importantly the BIOS) will be if > >> they get > >> shut down before i8042. Also there is EC which is in theory > >> independent > >> but in practice not so much. > > > > I see. > > > > Is this possible to identify ACPI devices that should wait for the > > i8042 > > suspend and that should be waited for by it on resume? > > We could try to add some dependencies while discovering PNP to get KBC > addresses in i8042 but we need tomake sure we do it even in presence > of i8042.nopnp. Well, I guess this is the example of the off-tree dependencies that actually matter Linus wanted. :-) I guess there are quite a few devices that can depend on the i8042 in principle, is this correct? Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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