| Message ID | 20180417104627.29643-1-l.stach@pengutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi all, Am Dienstag, den 17.04.2018, 12:46 +0200 schrieb Lucas Stach: > The current clock notifier sends an IPI to all CPUs, even if they are in > deep sleep state with the local timer disabled and switched to tick > broadcast. This needlessly cuts the CPU sleep times, as nothing is gained > from updating a disabled TWDs rate. > > Keep track of the enabled TWDs and only send an IPI to those CPUs with an > active local timer. As disabled TWDs may now miss a CPU frequency update > we need to make sure to refresh the rate on re-enabling of the timer. > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de> I would appreciate some feedback to this patch. FWIW, I've been running some systems with this patch applied for quite some time now with no issues spotted so far. Regards, Lucas > --- > arch/arm/kernel/smp_twd.c | 31 +++++++++++++++++++++++++++++-- > 1 file changed, 29 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c > index b30eafeef096..a3be30d30cc2 100644 > --- a/arch/arm/kernel/smp_twd.c > +++ b/arch/arm/kernel/smp_twd.c > @@ -32,6 +32,8 @@ static struct clk *twd_clk; > static unsigned long twd_timer_rate; > static DEFINE_PER_CPU(bool, percpu_setup_called); > > +static cpumask_var_t active_twd_mask; > + > static struct clock_event_device __percpu *twd_evt; > static unsigned int twd_features = > > CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; > @@ -39,12 +41,24 @@ static int twd_ppi; > > static int twd_shutdown(struct clock_event_device *clk) > { > > + cpumask_clear_cpu(smp_processor_id(), active_twd_mask); > + > > writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); > > return 0; > } > > static int twd_set_oneshot(struct clock_event_device *clk) > { > > + cpumask_set_cpu(smp_processor_id(), active_twd_mask); > + > > + /* > > + * When going from shutdown to oneshot we might have missed some > > + * frequency updates if the CPU was sleeping. Make sure to update > > + * the timer frequency with the current rate. > > + */ > > + if (clockevent_state_shutdown(clk)) > > + clockevents_update_freq(clk, twd_timer_rate); > + > > /* period set, and timer enabled in 'next_event' hook */ > > writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT, > > twd_base + TWD_TIMER_CONTROL); > @@ -57,6 +71,16 @@ static int twd_set_periodic(struct clock_event_device *clk) > > TWD_TIMER_CONTROL_IT_ENABLE | > > TWD_TIMER_CONTROL_PERIODIC; > > > + cpumask_set_cpu(smp_processor_id(), active_twd_mask); > + > > + /* > > + * When going from shutdown to periodic we might have missed some > > + * frequency updates if the CPU was sleeping. Make sure to update > > + * the timer frequency with the current rate. > > + */ > > + if (clockevent_state_shutdown(clk)) > > + clockevents_update_freq(clk, twd_timer_rate); > + > > writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ), > > twd_base + TWD_TIMER_LOAD); > > writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL); > @@ -124,8 +148,8 @@ static int twd_rate_change(struct notifier_block *nb, > > * changing cpu. > > */ > > if (flags == POST_RATE_CHANGE) > > - on_each_cpu(twd_update_frequency, > > - (void *)&cnd->new_rate, 1); > > + on_each_cpu_mask(active_twd_mask, twd_update_frequency, > > + (void *)&cnd->new_rate, 1); > > > return NOTIFY_OK; > } > @@ -326,6 +350,9 @@ static int __init twd_local_timer_common_register(struct device_node *np) > { > > int err; > > > + if (!zalloc_cpumask_var(&active_twd_mask, GFP_KERNEL)) > > + return -ENOMEM; > + > > twd_evt = alloc_percpu(struct clock_event_device); > > if (!twd_evt) { > > err = -ENOMEM;
Hi again, Am Montag, den 11.06.2018, 18:16 +0200 schrieb Lucas Stach: > Hi all, > > Am Dienstag, den 17.04.2018, 12:46 +0200 schrieb Lucas Stach: > > The current clock notifier sends an IPI to all CPUs, even if they are in > > deep sleep state with the local timer disabled and switched to tick > > broadcast. This needlessly cuts the CPU sleep times, as nothing is gained > > from updating a disabled TWDs rate. > > > > Keep track of the enabled TWDs and only send an IPI to those CPUs with an > > active local timer. As disabled TWDs may now miss a CPU frequency update > > we need to make sure to refresh the rate on re-enabling of the timer. > > > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de> > > I would appreciate some feedback to this patch. > FWIW, I've been running some systems with this patch applied for quite > some time now with no issues spotted so far. Can I persuade anyone to take a look at this? It's been some months since I've posted this and haven't got any feedback so far. I'm running this patch on a bunch of devices ever since posting it and could not spot any adverse effects. Regards, Lucas > > --- > > arch/arm/kernel/smp_twd.c | 31 +++++++++++++++++++++++++++++-- > > 1 file changed, 29 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c > > index b30eafeef096..a3be30d30cc2 100644 > > --- a/arch/arm/kernel/smp_twd.c > > +++ b/arch/arm/kernel/smp_twd.c > > @@ -32,6 +32,8 @@ static struct clk *twd_clk; > > static unsigned long twd_timer_rate; > > static DEFINE_PER_CPU(bool, percpu_setup_called); > > > > +static cpumask_var_t active_twd_mask; > > + > > static struct clock_event_device __percpu *twd_evt; > > static unsigned int twd_features = > > > CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; > > > > @@ -39,12 +41,24 @@ static int twd_ppi; > > > > static int twd_shutdown(struct clock_event_device *clk) > > { > > > + cpumask_clear_cpu(smp_processor_id(), active_twd_mask); > > > > + > > > > > > writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); > > > return 0; > > > > } > > > > static int twd_set_oneshot(struct clock_event_device *clk) > > { > > > + cpumask_set_cpu(smp_processor_id(), active_twd_mask); > > > > + > > > > > > + /* > > > > > > + * When going from shutdown to oneshot we might have missed some > > > > > > + * frequency updates if the CPU was sleeping. Make sure to update > > > > > > + * the timer frequency with the current rate. > > > > > > + */ > > > > > > + if (clockevent_state_shutdown(clk)) > > > + clockevents_update_freq(clk, twd_timer_rate); > > > > + > > > > > > /* period set, and timer enabled in 'next_event' hook */ > > > > > > writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT, > > > twd_base + TWD_TIMER_CONTROL); > > > > @@ -57,6 +71,16 @@ static int twd_set_periodic(struct clock_event_device *clk) > > > > > > TWD_TIMER_CONTROL_IT_ENABLE | > > > TWD_TIMER_CONTROL_PERIODIC; > > > > > > > + cpumask_set_cpu(smp_processor_id(), active_twd_mask); > > > > + > > > > > > + /* > > > > > > + * When going from shutdown to periodic we might have missed some > > > > > > + * frequency updates if the CPU was sleeping. Make sure to update > > > > > > + * the timer frequency with the current rate. > > > > > > + */ > > > > > > + if (clockevent_state_shutdown(clk)) > > > + clockevents_update_freq(clk, twd_timer_rate); > > > > + > > > > > > writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ), > > > > > > twd_base + TWD_TIMER_LOAD); > > > writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL); > > > > @@ -124,8 +148,8 @@ static int twd_rate_change(struct notifier_block *nb, > > > > > > * changing cpu. > > > > > > */ > > > > > > if (flags == POST_RATE_CHANGE) > > > > > > - on_each_cpu(twd_update_frequency, > > > > > > - (void *)&cnd->new_rate, 1); > > > > > > + on_each_cpu_mask(active_twd_mask, twd_update_frequency, > > > + (void *)&cnd->new_rate, 1); > > > > > > > return NOTIFY_OK; > > > > } > > @@ -326,6 +350,9 @@ static int __init twd_local_timer_common_register(struct device_node *np) > > { > > > int err; > > > > > > > > > > + if (!zalloc_cpumask_var(&active_twd_mask, GFP_KERNEL)) > > > + return -ENOMEM; > > > > + > > > > > > twd_evt = alloc_percpu(struct clock_event_device); > > > > > > if (!twd_evt) { > > > err = -ENOMEM; > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 29/10/2018 12:34, Lucas Stach wrote: > Hi again, > > Am Montag, den 11.06.2018, 18:16 +0200 schrieb Lucas Stach: >> Hi all, >> >> Am Dienstag, den 17.04.2018, 12:46 +0200 schrieb Lucas Stach: >>> The current clock notifier sends an IPI to all CPUs, even if they are in >>> deep sleep state with the local timer disabled and switched to tick >>> broadcast. This needlessly cuts the CPU sleep times, as nothing is gained >>> from updating a disabled TWDs rate. >>> >>> Keep track of the enabled TWDs and only send an IPI to those CPUs with an >>> active local timer. As disabled TWDs may now miss a CPU frequency update >>> we need to make sure to refresh the rate on re-enabling of the timer. >>> >>> Signed-off-by: Lucas Stach <l.stach@pengutronix.de> >> >> I would appreciate some feedback to this patch. >> FWIW, I've been running some systems with this patch applied for quite >> some time now with no issues spotted so far. > > Can I persuade anyone to take a look at this? > It's been some months since I've posted this and haven't got any > feedback so far. I'm running this patch on a bunch of devices ever > since posting it and could not spot any adverse effects. At the first glance, feature and code looks for me. -- Daniel
On Tue, 2018-04-17 at 12:46 +0200, Lucas Stach wrote: [...] > @@ -326,6 +350,9 @@ static int __init twd_local_timer_common_register(struct device_node *np) > { > int err; > > + if (!zalloc_cpumask_var(&active_twd_mask, GFP_KERNEL)) > + return -ENOMEM; > + > twd_evt = alloc_percpu(struct clock_event_device); > if (!twd_evt) { > err = -ENOMEM; This could free_cpumask_var(active_twd_mask) in the error path. regards Philipp
On Mon, Oct 29, 2018 at 12:34:48PM +0100, Lucas Stach wrote: > Hi again, > > Am Montag, den 11.06.2018, 18:16 +0200 schrieb Lucas Stach: > > Hi all, > > > > Am Dienstag, den 17.04.2018, 12:46 +0200 schrieb Lucas Stach: > > > The current clock notifier sends an IPI to all CPUs, even if they are in > > > deep sleep state with the local timer disabled and switched to tick > > > broadcast. This needlessly cuts the CPU sleep times, as nothing is gained > > > from updating a disabled TWDs rate. > > > > > > Keep track of the enabled TWDs and only send an IPI to those CPUs with an > > > active local timer. As disabled TWDs may now miss a CPU frequency update > > > we need to make sure to refresh the rate on re-enabling of the timer. > > > > > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de> > > > > I would appreciate some feedback to this patch. > > FWIW, I've been running some systems with this patch applied for quite > > some time now with no issues spotted so far. > > Can I persuade anyone to take a look at this? > It's been some months since I've posted this and haven't got any > feedback so far. I'm running this patch on a bunch of devices ever > since posting it and could not spot any adverse effects. This, quite simply, needs review by kernel/time people, especially given the potential recursion setup by adding calls to clockevents_update_freq() from within methods that this function _may_ call. For example, if the current state is shutdown, and clockevents_switch_state() is called to set periodic mode, __clockevents_switch_state() will be called to set periodic mode. The current mode will be shutdown. We'll call twd_set_periodic(), which will then call into clockevents_update_freq(). If tick_broadcast_update_freq() returns -ENODEV (I don't know under what situation that occurs), then we'll call __clockevents_update_freq(). This currently will avoid calling __clockevents_switch_state() but only because the current mode is not marked as periodic yet. If that changes (either by marking it periodic earlier, or __clockevents_update_freq() changes), then we get a situation where we'll call back into twd_set_periodic(). Then there's the ordering issues - what if we're switching to one-shot mode, does this mean we could get something like: - set one-shot mode - clockevents_update_freq - set next event - set stale next event So, I can't review this patch without spending a lot of time reading and understanding the kernel/time code. It would be way better if someone who does understand that code (iow, a maintainer of that code) looked at this patch. > > > --- > > > arch/arm/kernel/smp_twd.c | 31 +++++++++++++++++++++++++++++-- > > > 1 file changed, 29 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c > > > index b30eafeef096..a3be30d30cc2 100644 > > > --- a/arch/arm/kernel/smp_twd.c > > > +++ b/arch/arm/kernel/smp_twd.c > > > @@ -32,6 +32,8 @@ static struct clk *twd_clk; > > > static unsigned long twd_timer_rate; > > > static DEFINE_PER_CPU(bool, percpu_setup_called); > > > > > > +static cpumask_var_t active_twd_mask; > > > + > > > static struct clock_event_device __percpu *twd_evt; > > > static unsigned int twd_features = > > > > CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; > > > > > > @@ -39,12 +41,24 @@ static int twd_ppi; > > > > > > static int twd_shutdown(struct clock_event_device *clk) > > > { > > > > + cpumask_clear_cpu(smp_processor_id(), active_twd_mask); > > > > > > + > > > > > > > writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); > > > > return 0; > > > > > > } > > > > > > static int twd_set_oneshot(struct clock_event_device *clk) > > > { > > > > + cpumask_set_cpu(smp_processor_id(), active_twd_mask); > > > > > > + > > > > > > > + /* > > > > > > > + * When going from shutdown to oneshot we might have missed some > > > > > > > + * frequency updates if the CPU was sleeping. Make sure to update > > > > > > > + * the timer frequency with the current rate. > > > > > > > + */ > > > > > > > + if (clockevent_state_shutdown(clk)) > > > > + clockevents_update_freq(clk, twd_timer_rate); > > > > > > + > > > > > > > /* period set, and timer enabled in 'next_event' hook */ > > > > > > > writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT, > > > > twd_base + TWD_TIMER_CONTROL); > > > > > > @@ -57,6 +71,16 @@ static int twd_set_periodic(struct clock_event_device *clk) > > > > > > > TWD_TIMER_CONTROL_IT_ENABLE | > > > > TWD_TIMER_CONTROL_PERIODIC; > > > > > > > > > > + cpumask_set_cpu(smp_processor_id(), active_twd_mask); > > > > > > + > > > > > > > + /* > > > > > > > + * When going from shutdown to periodic we might have missed some > > > > > > > + * frequency updates if the CPU was sleeping. Make sure to update > > > > > > > + * the timer frequency with the current rate. > > > > > > > + */ > > > > > > > + if (clockevent_state_shutdown(clk)) > > > > + clockevents_update_freq(clk, twd_timer_rate); > > > > > > + > > > > > > > writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ), > > > > > > > twd_base + TWD_TIMER_LOAD); > > > > writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL); > > > > > > @@ -124,8 +148,8 @@ static int twd_rate_change(struct notifier_block *nb, > > > > > > > * changing cpu. > > > > > > > */ > > > > > > > if (flags == POST_RATE_CHANGE) > > > > > > > - on_each_cpu(twd_update_frequency, > > > > > > > - (void *)&cnd->new_rate, 1); > > > > > > > + on_each_cpu_mask(active_twd_mask, twd_update_frequency, > > > > + (void *)&cnd->new_rate, 1); > > > > > > > > > > return NOTIFY_OK; > > > > > > } > > > @@ -326,6 +350,9 @@ static int __init twd_local_timer_common_register(struct device_node *np) > > > { > > > > int err; > > > > > > > > > > > > > + if (!zalloc_cpumask_var(&active_twd_mask, GFP_KERNEL)) > > > > + return -ENOMEM; > > > > > > + > > > > > > > twd_evt = alloc_percpu(struct clock_event_device); > > > > > > > if (!twd_evt) { > > > > err = -ENOMEM; > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 29/10/2018 12:34, Lucas Stach wrote: > Hi again, > > Am Montag, den 11.06.2018, 18:16 +0200 schrieb Lucas Stach: >> Hi all, >> >> Am Dienstag, den 17.04.2018, 12:46 +0200 schrieb Lucas Stach: >>> The current clock notifier sends an IPI to all CPUs, even if they are in >>> deep sleep state with the local timer disabled and switched to tick >>> broadcast. This needlessly cuts the CPU sleep times, as nothing is gained >>> from updating a disabled TWDs rate. >>> >>> Keep track of the enabled TWDs and only send an IPI to those CPUs with an >>> active local timer. As disabled TWDs may now miss a CPU frequency update >>> we need to make sure to refresh the rate on re-enabling of the timer. >>> >>> Signed-off-by: Lucas Stach <l.stach@pengutronix.de> >> >> I would appreciate some feedback to this patch. >> FWIW, I've been running some systems with this patch applied for quite >> some time now with no issues spotted so far. > > Can I persuade anyone to take a look at this? > It's been some months since I've posted this and haven't got any > feedback so far. I'm running this patch on a bunch of devices ever > since posting it and could not spot any adverse effects. Hi Lucas, can you resend this patch (keeping the current recipient) but adding Thomas Gleixner and John Stultz, the maintainer of the time core framework. Thanks -- Daniel
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c index b30eafeef096..a3be30d30cc2 100644 --- a/arch/arm/kernel/smp_twd.c +++ b/arch/arm/kernel/smp_twd.c @@ -32,6 +32,8 @@ static struct clk *twd_clk; static unsigned long twd_timer_rate; static DEFINE_PER_CPU(bool, percpu_setup_called); +static cpumask_var_t active_twd_mask; + static struct clock_event_device __percpu *twd_evt; static unsigned int twd_features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; @@ -39,12 +41,24 @@ static int twd_ppi; static int twd_shutdown(struct clock_event_device *clk) { + cpumask_clear_cpu(smp_processor_id(), active_twd_mask); + writel_relaxed(0, twd_base + TWD_TIMER_CONTROL); return 0; } static int twd_set_oneshot(struct clock_event_device *clk) { + cpumask_set_cpu(smp_processor_id(), active_twd_mask); + + /* + * When going from shutdown to oneshot we might have missed some + * frequency updates if the CPU was sleeping. Make sure to update + * the timer frequency with the current rate. + */ + if (clockevent_state_shutdown(clk)) + clockevents_update_freq(clk, twd_timer_rate); + /* period set, and timer enabled in 'next_event' hook */ writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT, twd_base + TWD_TIMER_CONTROL); @@ -57,6 +71,16 @@ static int twd_set_periodic(struct clock_event_device *clk) TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_PERIODIC; + cpumask_set_cpu(smp_processor_id(), active_twd_mask); + + /* + * When going from shutdown to periodic we might have missed some + * frequency updates if the CPU was sleeping. Make sure to update + * the timer frequency with the current rate. + */ + if (clockevent_state_shutdown(clk)) + clockevents_update_freq(clk, twd_timer_rate); + writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ), twd_base + TWD_TIMER_LOAD); writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL); @@ -124,8 +148,8 @@ static int twd_rate_change(struct notifier_block *nb, * changing cpu. */ if (flags == POST_RATE_CHANGE) - on_each_cpu(twd_update_frequency, - (void *)&cnd->new_rate, 1); + on_each_cpu_mask(active_twd_mask, twd_update_frequency, + (void *)&cnd->new_rate, 1); return NOTIFY_OK; } @@ -326,6 +350,9 @@ static int __init twd_local_timer_common_register(struct device_node *np) { int err; + if (!zalloc_cpumask_var(&active_twd_mask, GFP_KERNEL)) + return -ENOMEM; + twd_evt = alloc_percpu(struct clock_event_device); if (!twd_evt) { err = -ENOMEM;
The current clock notifier sends an IPI to all CPUs, even if they are in deep sleep state with the local timer disabled and switched to tick broadcast. This needlessly cuts the CPU sleep times, as nothing is gained from updating a disabled TWDs rate. Keep track of the enabled TWDs and only send an IPI to those CPUs with an active local timer. As disabled TWDs may now miss a CPU frequency update we need to make sure to refresh the rate on re-enabling of the timer. Signed-off-by: Lucas Stach <l.stach@pengutronix.de> --- arch/arm/kernel/smp_twd.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-)