Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 05/14/2015 04:29 AM, Kevin Hilman wrote: Rafael J. Wysocki r...@rjwysocki.net writes: [...] Second, quite honestly, I don't see a connection to genpd here. The connection with genpd is because the *reason* the timer was shutdown/stopped is because it shares power with the CPU, which is why the timer stops when the CPU hits ceratin low power states. IOW, it's in the same power domain as the CPU. What you seem to be saying is maybe we can eliminate the need to check the return value of tick_broadcast_enter() in the idle loop if we proactively disable the TIMER_STOP idle states of a CPU when we start to use that CPU's timer as a broadcast one. So this seems to be about the timekeeping rather than power domains, because that's where the broadcast thing is done. So the code setting up the CPU's timer for broadcast would pretty much need to pause cpuidle, go through the CPU's idle states and disable the TIMER_STOP ones. And do the reverse when the timer is not going the be used for broadcast any more. Or..., modify the timer subystem to use runtime PM on the timer devices, create a genpd that includes the timer device, and use pm_genpd_attach_cpuidle() to attach that genpd so that whenever that timer is runtime PM active, the deeper C-states cannot be hit. I think you are missing a point here. If such a solution were possible, the tick broadcast framework would not have been designed to support deep cpu idle states. One reason we cannot go this way of course, is not all archs may support genpd as was pointed out. But the second reason IMO is that a timer is runtime PM active as long as there is some deferred work, either in the near or far future. The point behind the broadcast framework is let these CPUs go to deeper idle states when the timers are in the far future. We can potentially save power by doing so and don't need to keep the entire power domain active just because the timer is supposed to fire 5 minutes from now, which is precisely what happens if we go the genpd way. Hence I don't think we can trivially club timers with genpd unless we have a way to power the timer PM domain down, depending on when it is supposed to fire, in which case we will merely be replicating the cpuidle governor code. Regards Preeti U Murthy So question is whether or not this is actually really more straightforward than checking the return value of tick_broadcast_enter() in the idle loop after all. Unfortunetly this problem doesn't only affect timers. Daniel's broader point is that $SUBJECT series only handles this for the timer, but there's actually a more general problem to solve for *any* device that shares a power domain with a CPU (e.g. CPU-local timers, interrupt controllers, performance monitoring units, floating point units, etc. etc.) If we keep adding checks to the idle loop for all those devices, we're heading for a mess. (In fact, this is exactly what CPUidle drivers in lots of vendor trees are doing, and it is indeed quite messy, and very vendor specific.) Also, solving this more general problem was the primary motivation for adding the gnpd _attach_cpuidle() feature in the first place, so why not use that? Longer term, IMO, these dependencies between CPUs and all these extras logic that share a power domain should be modeled by a genpd. If all those devices are using runtime PM, including the CPUs, and they are grouped into a genpd, then we we can very easily know at the genpd level whether or not the CPU could be powered down, and to what level. This longer-term solution is what I want to discuss at LPC this year in my Unifiy idle management of CPUs and IO devices topic[1]. ( Also FYI, using a genpd to model a CPU and connected logic is part of the motivation behind the recent proposals to add support for multiple states to genpd by Axel Haslam. ) Anyways I digress... In the short term, while your patches look fine to me, the objection I have is that it's only a band-aid fix that handles timers, but none of the other extras that might share a power rail with the CPU. So, until we have the long-term stuff sorted out, the better short-term solution IMO is the _attach_cpuidle() one above. Kevin [1] http://wiki.linuxplumbersconf.org/2015:energy-aware_scheduling ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Wednesday, May 13, 2015 05:13:27 PM Kevin Hilman wrote: On Wed, May 13, 2015 at 5:16 PM, Rafael J. Wysocki r...@rjwysocki.net wrote: On Wednesday, May 13, 2015 03:59:55 PM Kevin Hilman wrote: Rafael J. Wysocki r...@rjwysocki.net writes: [...] Second, quite honestly, I don't see a connection to genpd here. The connection with genpd is because the *reason* the timer was shutdown/stopped is because it shares power with the CPU, which is why the timer stops when the CPU hits ceratin low power states. IOW, it's in the same power domain as the CPU. Well, what if you don't have genpd on that system? Is the problem at hand not relevant then magically? Well, if you're not using genpd to model hardware power domain dependencies, then yes you'll definitely need a different solution. And, as we discussed on IRC. If you only care about timers, and genpd is not in use, then $SUBJECT series is a fine approach, and I have no objections. But for SoCs where there are several other things that share power with CPU, we need a more generic, genpd based solution, which it seems we're in agreement on. And since the two approaches are not mutually exclusive, then I have real objections to applying this series. I guess a no is missing in the last sentence. ;-) Acked-by: Kevin Hilman khil...@linaro.org Thanks! Rafael ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Wednesday, May 13, 2015 03:59:55 PM Kevin Hilman wrote: Rafael J. Wysocki r...@rjwysocki.net writes: [...] Second, quite honestly, I don't see a connection to genpd here. The connection with genpd is because the *reason* the timer was shutdown/stopped is because it shares power with the CPU, which is why the timer stops when the CPU hits ceratin low power states. IOW, it's in the same power domain as the CPU. Well, what if you don't have genpd on that system? Is the problem at hand not relevant then magically? Rafael ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Wed, May 13, 2015 at 5:16 PM, Rafael J. Wysocki r...@rjwysocki.net wrote: On Wednesday, May 13, 2015 03:59:55 PM Kevin Hilman wrote: Rafael J. Wysocki r...@rjwysocki.net writes: [...] Second, quite honestly, I don't see a connection to genpd here. The connection with genpd is because the *reason* the timer was shutdown/stopped is because it shares power with the CPU, which is why the timer stops when the CPU hits ceratin low power states. IOW, it's in the same power domain as the CPU. Well, what if you don't have genpd on that system? Is the problem at hand not relevant then magically? Well, if you're not using genpd to model hardware power domain dependencies, then yes you'll definitely need a different solution. And, as we discussed on IRC. If you only care about timers, and genpd is not in use, then $SUBJECT series is a fine approach, and I have no objections. But for SoCs where there are several other things that share power with CPU, we need a more generic, genpd based solution, which it seems we're in agreement on. And since the two approaches are not mutually exclusive, then I have real objections to applying this series. Acked-by: Kevin Hilman khil...@linaro.org Kevin ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
Rafael J. Wysocki r...@rjwysocki.net writes: [...] Second, quite honestly, I don't see a connection to genpd here. The connection with genpd is because the *reason* the timer was shutdown/stopped is because it shares power with the CPU, which is why the timer stops when the CPU hits ceratin low power states. IOW, it's in the same power domain as the CPU. What you seem to be saying is maybe we can eliminate the need to check the return value of tick_broadcast_enter() in the idle loop if we proactively disable the TIMER_STOP idle states of a CPU when we start to use that CPU's timer as a broadcast one. So this seems to be about the timekeeping rather than power domains, because that's where the broadcast thing is done. So the code setting up the CPU's timer for broadcast would pretty much need to pause cpuidle, go through the CPU's idle states and disable the TIMER_STOP ones. And do the reverse when the timer is not going the be used for broadcast any more. Or..., modify the timer subystem to use runtime PM on the timer devices, create a genpd that includes the timer device, and use pm_genpd_attach_cpuidle() to attach that genpd so that whenever that timer is runtime PM active, the deeper C-states cannot be hit. So question is whether or not this is actually really more straightforward than checking the return value of tick_broadcast_enter() in the idle loop after all. Unfortunetly this problem doesn't only affect timers. Daniel's broader point is that $SUBJECT series only handles this for the timer, but there's actually a more general problem to solve for *any* device that shares a power domain with a CPU (e.g. CPU-local timers, interrupt controllers, performance monitoring units, floating point units, etc. etc.) If we keep adding checks to the idle loop for all those devices, we're heading for a mess. (In fact, this is exactly what CPUidle drivers in lots of vendor trees are doing, and it is indeed quite messy, and very vendor specific.) Also, solving this more general problem was the primary motivation for adding the gnpd _attach_cpuidle() feature in the first place, so why not use that? Longer term, IMO, these dependencies between CPUs and all these extras logic that share a power domain should be modeled by a genpd. If all those devices are using runtime PM, including the CPUs, and they are grouped into a genpd, then we we can very easily know at the genpd level whether or not the CPU could be powered down, and to what level. This longer-term solution is what I want to discuss at LPC this year in my Unifiy idle management of CPUs and IO devices topic[1]. ( Also FYI, using a genpd to model a CPU and connected logic is part of the motivation behind the recent proposals to add support for multiple states to genpd by Axel Haslam. ) Anyways I digress... In the short term, while your patches look fine to me, the objection I have is that it's only a band-aid fix that handles timers, but none of the other extras that might share a power rail with the CPU. So, until we have the long-term stuff sorted out, the better short-term solution IMO is the _attach_cpuidle() one above. Kevin [1] http://wiki.linuxplumbersconf.org/2015:energy-aware_scheduling ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
Rafael J. Wysocki r...@rjwysocki.net writes: On Wednesday, May 13, 2015 05:13:27 PM Kevin Hilman wrote: On Wed, May 13, 2015 at 5:16 PM, Rafael J. Wysocki r...@rjwysocki.net wrote: On Wednesday, May 13, 2015 03:59:55 PM Kevin Hilman wrote: Rafael J. Wysocki r...@rjwysocki.net writes: [...] Second, quite honestly, I don't see a connection to genpd here. The connection with genpd is because the *reason* the timer was shutdown/stopped is because it shares power with the CPU, which is why the timer stops when the CPU hits ceratin low power states. IOW, it's in the same power domain as the CPU. Well, what if you don't have genpd on that system? Is the problem at hand not relevant then magically? Well, if you're not using genpd to model hardware power domain dependencies, then yes you'll definitely need a different solution. And, as we discussed on IRC. If you only care about timers, and genpd is not in use, then $SUBJECT series is a fine approach, and I have no objections. But for SoCs where there are several other things that share power with CPU, we need a more generic, genpd based solution, which it seems we're in agreement on. And since the two approaches are not mutually exclusive, then I have real objections to applying this series. I guess a no is missing in the last sentence. ;-) Correct. I have *no* real objections to applying this series. Kevin ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 05/12/2015 01:31 AM, Rafael J. Wysocki wrote: On Monday, May 11, 2015 07:40:41 PM Daniel Lezcano wrote: On 05/10/2015 01:15 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. IMO the resulting code is more and more confusing. Why is it confusing? What part of it is confusing? Patches [1-2/3] simply replace https://patchwork.kernel.org/patch/6326761/ and I'm not sure why that would be confusing. Patch [3/3] simply causes cpuidle_enter_state() to pick up a more suitable state if tick_broadcast_enter() fails instead of returning an error code in that case. What exactly is confusing in that? Except I miss something, the tick_broadcast_enter can fail only if the local timer of the current cpu is used as a broadcast timer (which is the case today for PPC only). well, why does this matter? The correct fix would be to tie this local timer with the cpu power domain and disable the idle state powering down this domain like it was done for the renesas cpuidle driver. IOW, the cpu power domain is in use (because of its local timer), so we shouldn't shut it down. No ? Sorry, I'm not sure what you're talking about. The problem at hand is that tick_broadcast_enter() can fail and we need to handle that. If we can prevent it from ever failing, that would be awesome, but quite honestly I don't see how to do that ATM. Ok, sorry. Let me clarify. You did a mechanism two years ago with pm_genpd_attach_cpuidle and power_on/off. That disables a cpuidle state when a power domain is in use. The idea I was proposing is to reuse this approach. The logic is: The local timer is in use, this idle state power downs this timer, then disable it. So it is when the broadcast timer is 'bound_on' a cpu, we disable the idle states. That could be done via a loop looking for the TIMER_STOP flag or via the power domain. Hence the cpuidle_select will never return a state which powers downs the local cpu (because they are disabled) and tick_broadcast_enter can't fail because it is never called. Does it make more sense ? I am aware this is not easily fixable because the genpd framework is incomplete and has some restrictions but I believe it is worth to have a discussion. Add Kevin and Ulf in Cc. So I'm going to queue up these patches for 4.2 and we can have a discussion just fine regardless. -- http://www.linaro.org/ Linaro.org │ Open source software for ARM SoCs Follow Linaro: http://www.facebook.com/pages/Linaro Facebook | http://twitter.com/#!/linaroorg Twitter | http://www.linaro.org/linaro-blog/ Blog ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 05/12/2015 03:23 PM, Rafael J. Wysocki wrote: On Tuesday, May 12, 2015 10:41:35 AM Daniel Lezcano wrote: On 05/12/2015 01:31 AM, Rafael J. Wysocki wrote: On Monday, May 11, 2015 07:40:41 PM Daniel Lezcano wrote: On 05/10/2015 01:15 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. IMO the resulting code is more and more confusing. Why is it confusing? What part of it is confusing? Patches [1-2/3] simply replace https://patchwork.kernel.org/patch/6326761/ and I'm not sure why that would be confusing. Patch [3/3] simply causes cpuidle_enter_state() to pick up a more suitable state if tick_broadcast_enter() fails instead of returning an error code in that case. What exactly is confusing in that? Except I miss something, the tick_broadcast_enter can fail only if the local timer of the current cpu is used as a broadcast timer (which is the case today for PPC only). well, why does this matter? The correct fix would be to tie this local timer with the cpu power domain and disable the idle state powering down this domain like it was done for the renesas cpuidle driver. IOW, the cpu power domain is in use (because of its local timer), so we shouldn't shut it down. No ? Sorry, I'm not sure what you're talking about. The problem at hand is that tick_broadcast_enter() can fail and we need to handle that. If we can prevent it from ever failing, that would be awesome, but quite honestly I don't see how to do that ATM. Ok, sorry. Let me clarify. You did a mechanism two years ago with pm_genpd_attach_cpuidle and power_on/off. That disables a cpuidle state when a power domain is in use. The idea I was proposing is to reuse this approach. The logic is: The local timer is in use, this idle state power downs this timer, then disable it. I'm not sure it's about powering down. Stopping rather (which may or may not involve powering down). So it is when the broadcast timer is 'bound_on' a cpu, we disable the idle states. That could be done via a loop looking for the TIMER_STOP flag or via the power domain. Hence the cpuidle_select will never return a state which powers downs the local cpu (because they are disabled) and tick_broadcast_enter can't fail because it is never called. Does it make more sense ? Well, you've not explained what's confusing in the code after this series in the first place. :-) It is not the series itself but the sum of the recent changes in this area makes the overall more and more difficult to maintain. But that's a personal opinion. Sounds like we are trying to catch the corner cases each time there is a change somewhere. Second, quite honestly, I don't see a connection to genpd here. Probably I am not clear :) The connection we have is the local timer and the cpuidle framework shutting it down. Why ? Because the local timer belongs to the cpu's power domain. Using the genpd to describe this relation between an idle state and the devices impacted by via a power domain is, in my opinion, a nice abstraction and a good opportunity to integrate the different subsystems. Furthermore it is consistent with Kevin's investigation around the power domain and SoC idle. Kevin ? What you seem to be saying is maybe we can eliminate the need to check the return value of tick_broadcast_enter() in the idle loop if we proactively disable the TIMER_STOP idle states of a CPU when we start to use that CPU's timer as a broadcast one. Well, not exactly. That's the consequence. I meant, using any devices in a specific power domain makes impossible to
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Tuesday, May 12, 2015 10:41:35 AM Daniel Lezcano wrote: On 05/12/2015 01:31 AM, Rafael J. Wysocki wrote: On Monday, May 11, 2015 07:40:41 PM Daniel Lezcano wrote: On 05/10/2015 01:15 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] +/* Take note of the planned idle state. */ +idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. IMO the resulting code is more and more confusing. Why is it confusing? What part of it is confusing? Patches [1-2/3] simply replace https://patchwork.kernel.org/patch/6326761/ and I'm not sure why that would be confusing. Patch [3/3] simply causes cpuidle_enter_state() to pick up a more suitable state if tick_broadcast_enter() fails instead of returning an error code in that case. What exactly is confusing in that? Except I miss something, the tick_broadcast_enter can fail only if the local timer of the current cpu is used as a broadcast timer (which is the case today for PPC only). well, why does this matter? The correct fix would be to tie this local timer with the cpu power domain and disable the idle state powering down this domain like it was done for the renesas cpuidle driver. IOW, the cpu power domain is in use (because of its local timer), so we shouldn't shut it down. No ? Sorry, I'm not sure what you're talking about. The problem at hand is that tick_broadcast_enter() can fail and we need to handle that. If we can prevent it from ever failing, that would be awesome, but quite honestly I don't see how to do that ATM. Ok, sorry. Let me clarify. You did a mechanism two years ago with pm_genpd_attach_cpuidle and power_on/off. That disables a cpuidle state when a power domain is in use. The idea I was proposing is to reuse this approach. The logic is: The local timer is in use, this idle state power downs this timer, then disable it. I'm not sure it's about powering down. Stopping rather (which may or may not involve powering down). So it is when the broadcast timer is 'bound_on' a cpu, we disable the idle states. That could be done via a loop looking for the TIMER_STOP flag or via the power domain. Hence the cpuidle_select will never return a state which powers downs the local cpu (because they are disabled) and tick_broadcast_enter can't fail because it is never called. Does it make more sense ? Well, you've not explained what's confusing in the code after this series in the first place. :-) Second, quite honestly, I don't see a connection to genpd here. What you seem to be saying is maybe we can eliminate the need to check the return value of tick_broadcast_enter() in the idle loop if we proactively disable the TIMER_STOP idle states of a CPU when we start to use that CPU's timer as a broadcast one. So this seems to be about the timekeeping rather than power domains, because that's where the broadcast thing is done. So the code setting up the CPU's timer for broadcast would pretty much need to pause cpuidle, go through the CPU's idle states and disable the TIMER_STOP ones. And do the reverse when the timer is not going the be used for broadcast any more. So question is whether or not this is actually really more straightforward than checking the return value of tick_broadcast_enter() in the idle loop after all. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 10/05/15 00:15, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. Tested on ARM Vexpress platforms with one of the CPU in broadcast mode and also with broadcast timer. So, you can add: Tested-by: Sudeep Holla sudeep.ho...@arm.com Regards, Sudeep ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Monday, May 11, 2015 10:51:02 AM Preeti U Murthy wrote: On 05/10/2015 04:45 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. The patches look good. Based and tested these patches on top of linux-pm/linux-next (They are not yet in the branch as far as I can see.) They aren't in the tree yet. I'll put them in there later today. All patches in this series Reviewed and Tested-by: Preeti U Murthy pre...@linux.vnet.ibm.com Thanks! ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Monday, May 11, 2015 04:13:37 PM Sudeep Holla wrote: On 10/05/15 00:15, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. Tested on ARM Vexpress platforms with one of the CPU in broadcast mode and also with broadcast timer. So, you can add: Tested-by: Sudeep Holla sudeep.ho...@arm.com Thanks! ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Monday, May 11, 2015 07:40:41 PM Daniel Lezcano wrote: On 05/10/2015 01:15 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. IMO the resulting code is more and more confusing. Why is it confusing? What part of it is confusing? Patches [1-2/3] simply replace https://patchwork.kernel.org/patch/6326761/ and I'm not sure why that would be confusing. Patch [3/3] simply causes cpuidle_enter_state() to pick up a more suitable state if tick_broadcast_enter() fails instead of returning an error code in that case. What exactly is confusing in that? Except I miss something, the tick_broadcast_enter can fail only if the local timer of the current cpu is used as a broadcast timer (which is the case today for PPC only). well, why does this matter? The correct fix would be to tie this local timer with the cpu power domain and disable the idle state powering down this domain like it was done for the renesas cpuidle driver. IOW, the cpu power domain is in use (because of its local timer), so we shouldn't shut it down. No ? Sorry, I'm not sure what you're talking about. The problem at hand is that tick_broadcast_enter() can fail and we need to handle that. If we can prevent it from ever failing, that would be awesome, but quite honestly I don't see how to do that ATM. I am aware this is not easily fixable because the genpd framework is incomplete and has some restrictions but I believe it is worth to have a discussion. Add Kevin and Ulf in Cc. So I'm going to queue up these patches for 4.2 and we can have a discussion just fine regardless. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 05/10/2015 01:15 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. IMO the resulting code is more and more confusing. Except I miss something, the tick_broadcast_enter can fail only if the local timer of the current cpu is used as a broadcast timer (which is the case today for PPC only). The correct fix would be to tie this local timer with the cpu power domain and disable the idle state powering down this domain like it was done for the renesas cpuidle driver. IOW, the cpu power domain is in use (because of its local timer), so we shouldn't shut it down. No ? I am aware this is not easily fixable because the genpd framework is incomplete and has some restrictions but I believe it is worth to have a discussion. Add Kevin and Ulf in Cc. -- Daniel -- http://www.linaro.org/ Linaro.org │ Open source software for ARM SoCs Follow Linaro: http://www.facebook.com/pages/Linaro Facebook | http://twitter.com/#!/linaroorg Twitter | http://www.linaro.org/linaro-blog/ Blog ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 05/10/2015 04:45 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] +/* Take note of the planned idle state. */ +idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. I don't see the patches on linux-pm/linux-next. Regards Preeti U Murthy ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On 05/10/2015 04:45 AM, Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] +/* Take note of the planned idle state. */ +idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. The patches look good. Based and tested these patches on top of linux-pm/linux-next (They are not yet in the branch as far as I can see.) All patches in this series Reviewed and Tested-by: Preeti U Murthy pre...@linux.vnet.ibm.com ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures
On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote: On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote: Hi Rafael, On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote: [cut] + /* Take note of the planned idle state. */ + idle_set_state(smp_processor_id(), target_state); And I wouldn't do this either. The behavior here is pretty much as though the driver demoted the state chosen by the governor and we don't call idle_set_state() again in those cases. Why is this wrong? It is not wrong, but incomplete, because demotions done by the cpuidle driver should also be taken into account in the same way. But I'm seeing that the recent patch of mine that made cpuidle_enter_state() call default_idle_call() was a mistake, because it might confuse find_idlest_cpu() significantly as to what state the CPU is in. I'll drop that one for now. OK, done. So after I've dropped it I think we need to do three things: (1) Move the idle_set_state() calls to cpuidle_enter_state(). (2) Make cpuidle_enter_state() call default_idle_call() again, but this time do that *before* it has called idle_set_state() for target_state. (3) Introduce demotion as per my last patch. Let me cut patches for that. Done as per the above and the patches follow in replies to this messge. All on top of the current linux-next branch of the linux-pm.git tree. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
