Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates | From | Claudio Scordino <> | Date | Tue, 6 Feb 2018 19:14:28 +0100 |
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Hi Patrick,
Il 06/02/2018 16:43, Patrick Bellasi ha scritto: > Hi Claudio, > > On 06-Feb 11:55, Claudio Scordino wrote: >> Hi Peter, >> >> Il 20/12/2017 16:30, Peter Zijlstra ha scritto: >>> >>> So I ended up with the below (on top of Juri's cpufreq-dl patches). >>> >>> It compiles, but that's about all the testing it had. >>> >>> --- a/include/linux/sched/cpufreq.h >>> +++ b/include/linux/sched/cpufreq.h > > [..] > >>> @@ -188,17 +187,23 @@ static void sugov_get_util(struct sugov_ >>> static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu) >>> { >>> + unsigned long util = sg_cpu->util_cfs + sg_cpu->util_dl; >>> + struct rq *rq = cpu_rq(sg_cpu->cpu); >>> + >>> + if (rq->rt.rt_nr_running) >>> + util = sg_cpu->max; >>> + >>> /* >>> * Ideally we would like to set util_dl as min/guaranteed freq and >>> * util_cfs + util_dl as requested freq. However, cpufreq is not yet >>> * ready for such an interface. So, we only do the latter for now. >>> */ >>> - return min(sg_cpu->util_cfs + sg_cpu->util_dl, sg_cpu->max); >>> + return min(util, sg_cpu->max); >>> } > > [...] > >> >> What is the status of this patch ? I couldn't find it on the >> tip/queue repositories. >> >> BTW, I wonder if we actually want to remove also the information >> about the scheduling class who triggered the frequency change. > > Removing flags was the main goal of the patch, since they represents > mainly duplicated information which scheduling classes already know. > > This was making flags update error prone and difficult to keep > aligned with existing scheduling classes info. > >> This prevents us from adopting class-specific behaviors. > > In Peter's proposal he replaces flags with checks like: > > if (rq->rt.rt_nr_running) > >> For example, we might want to skip the rate limits when deadline >> asks for an increase of frequency, as shown in the patch below. >> In this case, we could just remove the flags from sugov_cpu, but >> leave the defines and the argument for sugov_update_*() > > At first glance, your proposal below makes to make sense. > > However, I'm wondering if we cannot get it working using > rq->dl's provided information instead of flags?
Yes, we can use the value of rq->dl to check if there has been an increase of the deadline utilization. Even if schedutil might have been triggered by a different scheduling class, the effect should be almost the same.
Below a potential patch. I've kept all frequency update decisions in a single point (i.e. sugov_should_update_freq). Not yet tested (waiting for further comments).
Thanks,
Claudio
From 49a6eec60574ae93297406d40155e6ce4113e442 Mon Sep 17 00:00:00 2001 From: Claudio Scordino <claudio@evidence.eu.com> Date: Tue, 6 Feb 2018 18:42:23 +0100 Subject: [PATCH] cpufreq: schedutil: rate limits for SCHED_DEADLINE
When the SCHED_DEADLINE scheduling class asks to increase the CPU frequency, we should not wait the rate limit, otherwise we may miss some deadline.
This patch moves all frequency update decisions to a single point: sugov_should_update_freq(). In addition, it ignores the rate limit whenever there is an increase of the CPU frequency given by an increase of the deadline utilization.
Signed-off-by: Claudio Scordino <claudio@evidence.eu.com> --- kernel/sched/cpufreq_schedutil.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index b0bd77d..e8504f5 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -74,7 +74,11 @@ static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu); /************************ Governor internals ***********************/ -static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time) +static bool sugov_should_update_freq(struct sugov_policy *sg_policy, + u64 time, + struct sugov_cpu *sg_cpu_old, + struct sugov_cpu *sg_cpu_new, + unsigned int next_freq) { s64 delta_ns; @@ -111,6 +115,14 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time) return true; } + /* + * Ignore rate limit when DL asked to increase the CPU frequency, + * otherwise we may miss some deadline. + */ + if ((next_freq > sg_policy->next_freq) && + (sg_cpu_new->util_dl > sg_cpu_old->util_dl)) + return true; + delta_ns = time - sg_policy->last_freq_update_time; return delta_ns >= sg_policy->freq_update_delay_ns; } @@ -271,6 +283,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, unsigned int flags) { struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util); + struct sugov_cpu sg_cpu_old = *sg_cpu; struct sugov_policy *sg_policy = sg_cpu->sg_policy; unsigned long util, max; unsigned int next_f; @@ -279,9 +292,6 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, sugov_set_iowait_boost(sg_cpu, time, flags); sg_cpu->last_update = time; - if (!sugov_should_update_freq(sg_policy, time)) - return; - busy = sugov_cpu_is_busy(sg_cpu); sugov_get_util(sg_cpu); @@ -300,7 +310,8 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, sg_policy->cached_raw_freq = 0; } - sugov_update_commit(sg_policy, time, next_f); + if (sugov_should_update_freq(sg_policy, time, &sg_cpu_old, sg_cpu, next_f)) + sugov_update_commit(sg_policy, time, next_f); } static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) @@ -350,6 +361,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time, unsigned int flags) { struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util); + struct sugov_cpu sg_cpu_old = *sg_cpu; struct sugov_policy *sg_policy = sg_cpu->sg_policy; unsigned int next_f; @@ -359,10 +371,9 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time, sugov_set_iowait_boost(sg_cpu, time, flags); sg_cpu->last_update = time; - if (sugov_should_update_freq(sg_policy, time)) { - next_f = sugov_next_freq_shared(sg_cpu, time); + next_f = sugov_next_freq_shared(sg_cpu, time); + if (sugov_should_update_freq(sg_policy, time, &sg_cpu_old, sg_cpu, next_f)) sugov_update_commit(sg_policy, time, next_f); - } raw_spin_unlock(&sg_policy->update_lock); } -- 2.7.4
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