[PATCH 0/8] Suspend block api (version 8)
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From: Florian Mickler on 3 Jun 2010 12:10 On Thu, 03 Jun 2010 10:29:52 -0500 James Bottomley <James.Bottomley(a)suse.de> wrote: > > So no reinvention. Just using a common scheme. > > By reinvention I meant open coding a common pattern for which the kernel > already has an API. (Whether we go with hash buckets or plists). > > James > Ah, plists.h! Thanks for the pointer. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Kevin Hilman on 3 Jun 2010 13:00 "Gross, Mark" <mark.gross(a)intel.com> writes: >>-----Original Message----- >>From: Kevin Hilman [mailto:khilman(a)deeprootsystems.com] >>Sent: Thursday, June 03, 2010 7:43 AM >>To: Peter Zijlstra >>Cc: Alan Cox; Gross, Mark; Florian Mickler; James Bottomley; Arve >>Hj�nnev�g; Neil Brown; tytso(a)mit.edu; LKML; Thomas Gleixner; Linux OMAP >>Mailing List; Linux PM; felipe.balbi(a)nokia.com >>Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) >> >>Peter Zijlstra <peterz(a)infradead.org> writes: >> >>> On Thu, 2010-06-03 at 11:03 +0100, Alan Cox wrote: >>>> > [mtg: ] This has been a pain point for the PM_QOS implementation. >>>> They change the constrain back and forth at the transaction level of >>>> the i2c driver. The pm_qos code really wasn't made to deal with such >>>> hot path use, as each such change triggers a re-computation of what >>>> the aggregate qos request is. >>>> >>>> That should be trivial in the usual case because 99% of the time you can >>>> hot path >>>> >>>> the QoS entry changing is the latest one >>>> there have been no other changes >>>> If it is valid I can use the cached previous aggregate I cunningly >>>> saved in the top QoS entry when I computed the new one >>>> >>>> (ie most of the time from the kernel side you have a QoS stack) >>> >>> Why would the kernel change the QoS state of a task? Why not have two >>> interacting QoS variables, one for the task, one for the subsystem in >>> question, and the action depends on their relative value? >> >>Yes, having a QoS parameter per-subsystem (or even per-device) is very >>important for SoCs that have independently controlled powerdomains. >>If all devices/subsystems in a particular powerdomain have QoS >>parameters that permit, the power state of that powerdomain can be >>lowered independently from system-wide power state and power states of >>other power domains. >> > This seems similar to that pm_qos generalization into bus drivers we where > waving our hands at during the collab summit in April? We never did get > into meaningful detail at that time. The hand-waving was around how to generalize it into the driver-model, or PM QoS. We're already doing this for OMAP, but in an OMAP-specific way, but it's become clear that this is something useful to generalize. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: James Bottomley on 3 Jun 2010 13:10 On Thu, 2010-06-03 at 09:58 -0700, Kevin Hilman wrote: > "Gross, Mark" <mark.gross(a)intel.com> writes: > > >>-----Original Message----- > >>From: Kevin Hilman [mailto:khilman(a)deeprootsystems.com] > >>Sent: Thursday, June 03, 2010 7:43 AM > >>To: Peter Zijlstra > >>Cc: Alan Cox; Gross, Mark; Florian Mickler; James Bottomley; Arve > >>Hjønnevåg; Neil Brown; tytso(a)mit.edu; LKML; Thomas Gleixner; Linux OMAP > >>Mailing List; Linux PM; felipe.balbi(a)nokia.com > >>Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) > >> > >>Peter Zijlstra <peterz(a)infradead.org> writes: > >> > >>> On Thu, 2010-06-03 at 11:03 +0100, Alan Cox wrote: > >>>> > [mtg: ] This has been a pain point for the PM_QOS implementation. > >>>> They change the constrain back and forth at the transaction level of > >>>> the i2c driver. The pm_qos code really wasn't made to deal with such > >>>> hot path use, as each such change triggers a re-computation of what > >>>> the aggregate qos request is. > >>>> > >>>> That should be trivial in the usual case because 99% of the time you can > >>>> hot path > >>>> > >>>> the QoS entry changing is the latest one > >>>> there have been no other changes > >>>> If it is valid I can use the cached previous aggregate I cunningly > >>>> saved in the top QoS entry when I computed the new one > >>>> > >>>> (ie most of the time from the kernel side you have a QoS stack) > >>> > >>> Why would the kernel change the QoS state of a task? Why not have two > >>> interacting QoS variables, one for the task, one for the subsystem in > >>> question, and the action depends on their relative value? > >> > >>Yes, having a QoS parameter per-subsystem (or even per-device) is very > >>important for SoCs that have independently controlled powerdomains. > >>If all devices/subsystems in a particular powerdomain have QoS > >>parameters that permit, the power state of that powerdomain can be > >>lowered independently from system-wide power state and power states of > >>other power domains. > >> > > This seems similar to that pm_qos generalization into bus drivers we where > > waving our hands at during the collab summit in April? We never did get > > into meaningful detail at that time. > > The hand-waving was around how to generalize it into the driver-model, > or PM QoS. We're already doing this for OMAP, but in an OMAP-specific > way, but it's become clear that this is something useful to > generalize. Do you have a pointer to the source and description? It might be useful to look at to do a reality check on what we're talking about. James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Muralidhar, Rajeev D on 3 Jun 2010 13:40 Hi Kevin, Mark, all, Yes, from our brief discussions at ELC, and all the ensuing discussions that have happened in the last few weeks, it certainly seems like a good time to think about: - what is a good model to tie up device idleness, latencies, constraints with cpu idle infrastructure - extensions to PM_QOS, part of what is being discussed, especially Kevin's earlier mail about QOS parameter per subsystem/device that may have independent clock/power domain control. - what is a good infrastructure to subsequently allow platform-specific low power state - extensions to cpuidle infrastructure to allow platform-wide low power state? Exact conditions for such entry/exit into low power state (latency, wake, etc.) could be platform specific. Is it a good idea to discuss about a model that could be applicable to other SOCs/platforms as well? Thanks Rajeev -----Original Message----- From: linux-pm-bounces(a)lists.linux-foundation.org [mailto:linux-pm-bounces(a)lists.linux-foundation.org] On Behalf Of Kevin Hilman Sent: Thursday, June 03, 2010 10:28 PM To: Gross, Mark Cc: Neil Brown; tytso(a)mit.edu; Peter Zijlstra; felipe.balbi(a)nokia.com; LKML; Florian Mickler; James Bottomley; Thomas Gleixner; Linux OMAP Mailing List; Linux PM; Alan Cox Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) "Gross, Mark" <mark.gross(a)intel.com> writes: >>-----Original Message----- >>From: Kevin Hilman [mailto:khilman(a)deeprootsystems.com] >>Sent: Thursday, June 03, 2010 7:43 AM >>To: Peter Zijlstra >>Cc: Alan Cox; Gross, Mark; Florian Mickler; James Bottomley; Arve >>Hj�nnev�g; Neil Brown; tytso(a)mit.edu; LKML; Thomas Gleixner; Linux OMAP >>Mailing List; Linux PM; felipe.balbi(a)nokia.com >>Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) >> >>Peter Zijlstra <peterz(a)infradead.org> writes: >> >>> On Thu, 2010-06-03 at 11:03 +0100, Alan Cox wrote: >>>> > [mtg: ] This has been a pain point for the PM_QOS implementation. >>>> They change the constrain back and forth at the transaction level of >>>> the i2c driver. The pm_qos code really wasn't made to deal with such >>>> hot path use, as each such change triggers a re-computation of what >>>> the aggregate qos request is. >>>> >>>> That should be trivial in the usual case because 99% of the time you can >>>> hot path >>>> >>>> the QoS entry changing is the latest one >>>> there have been no other changes >>>> If it is valid I can use the cached previous aggregate I cunningly >>>> saved in the top QoS entry when I computed the new one >>>> >>>> (ie most of the time from the kernel side you have a QoS stack) >>> >>> Why would the kernel change the QoS state of a task? Why not have two >>> interacting QoS variables, one for the task, one for the subsystem in >>> question, and the action depends on their relative value? >> >>Yes, having a QoS parameter per-subsystem (or even per-device) is very >>important for SoCs that have independently controlled powerdomains. >>If all devices/subsystems in a particular powerdomain have QoS >>parameters that permit, the power state of that powerdomain can be >>lowered independently from system-wide power state and power states of >>other power domains. >> > This seems similar to that pm_qos generalization into bus drivers we where > waving our hands at during the collab summit in April? We never did get > into meaningful detail at that time. The hand-waving was around how to generalize it into the driver-model, or PM QoS. We're already doing this for OMAP, but in an OMAP-specific way, but it's become clear that this is something useful to generalize. Kevin _______________________________________________ linux-pm mailing list linux-pm(a)lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/linux-pm -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Rafael J. Wysocki on 3 Jun 2010 17:10
On Thursday 03 June 2010, James Bottomley wrote: > On Thu, 2010-06-03 at 00:10 -0700, Arve Hjønnevåg wrote: > > On Wed, Jun 2, 2010 at 10:40 PM, mark gross <640e9920(a)gmail.com> wrote: > > > On Wed, Jun 02, 2010 at 09:54:15PM -0700, Brian Swetland wrote: > > >> On Wed, Jun 2, 2010 at 8:18 PM, mark gross <640e9920(a)gmail.com> wrote: > > >> > On Wed, Jun 02, 2010 at 02:58:30PM -0700, Arve Hjønnevåg wrote: > > >> >> > > >> >> The list is not short. You have all the inactive and active > > >> >> constraints on the same list. If you change it to a two level list > > >> >> though, the list of unique values (which is the list you have to walk) > > >> >> may be short enough for a tree to be overkill. > > >> > > > >> > what have you seen in practice from the wake-lock stats? > > >> > > > >> > I'm having a hard time seeing where you could get more than just a > > >> > handfull. However; one could go to a dual list (like the scheduler) and > > >> > move inactive nodes from an active to inactive list, or we could simply > > >> > remove them from the list uppon inactivity. which would would well > > >> > after I change the api to have the client allocate the memory for the > > >> > nodes... BUT, if your moving things in and out of a list a lot, I'm not > > >> > sure the break even point where changing the structure helps. > > >> > > > >> > We'll need to try it. > > >> > > > >> > I think we will almost never see more than 10 list elements. > > >> > > > >> > --mgross > > >> > > > >> > > > >> > > >> I see about 80 (based on the batteryinfo dump) on my Nexus One > > >> (QSD8250, Android Froyo): > > > > > > shucks. > > > > > > well I think for a pm_qos class that has boolean dynamic range we can > > > get away with not walking the list on every request update. we can use > > > a counter, and the list will be for mostly for stats. > > > > > > > Did you give any thought to my suggestion to only use one entry per > > unique value on the first level list and then use secondary lists of > > identical values. That way if you only have two constraints values the > > list you have to walk when updating a request will never have more > > than two entries regardless of how many total request you have. > > > > A request update then becomes something like this: > > if on primary list { > > unlink from primary list > > if secondary list is not empty > > get next secondary entry and add in same spot on primary list > > } > > unlink from secondary list > > find new spot on primary list > > if already there > > add to secondary list > > else > > add to primary list > > This is just reinventing hash bucketed lists. To get the benefits, all > we do is implement an N state constraint as backed by an N bucketed hash > list, which the kernel already has all the internal mechanics for. Agreed. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |