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Date: Sat, 19 Dec 2009 15:22:20 -0800 From: Dmitry Torokhov <dmitry.torokhov@...il.com> To: "Rafael J. Wysocki" <rjw@...k.pl> 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 Dec 19, 2009, at 3:10 PM, "Rafael J. Wysocki" <rjw@...k.pl> wrote: > 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? The devices that depend on i8042 are serio ports that are it's children. I8042 itself may have indirect dependency on a couple of PNP devices. > I hope this answers your question... -- Dmitry -- 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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