Messages in this thread | | | From | Vincent Guittot <> | Date | Fri, 11 Sep 2015 16:45:49 +0200 | Subject | Re: [PATCH 2/6] sched/fair: Convert arch_scale_cpu_capacity() from weak function to #define |
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On 11 September 2015 at 15:21, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > On 04/09/15 08:26, Vincent Guittot wrote: >> On 3 September 2015 at 21:58, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > [...] > >> So, with the patch below that updates the arm definition of >> arch_scale_cpu_capacity, you can add my Acked-by: Vincent Guittot >> <vincent.guittot@linaro.org> on this patch and the additional one >> below > > My tests on ARM TC2 (only the 2 A15's) show that the influence of the > non-default arch_scale_cpu_capacity function in > arch/arm/kernel/topology.c and with it the extra function call to it > from __update_load_avg() has no measurable influence on performance: > > perf stat --null --repeat 10 -- perf bench sched messaging --g 50 -l 200 > > - default arch_scale_cpu_capacity function [kernel/sched/sched.h] > > 16.006976251 seconds time elapsed ( +- 0.29% ) > 16.063814914 seconds time elapsed ( +- 0.37% ) > 16.088199252 seconds time elapsed ( +- 0.39% ) > > - arch_scale_cpu_capacity function [arch/arm/kernel/topology.c] > > 15.945975308 seconds time elapsed ( +- 0.10% ) > 16.131203074 seconds time elapsed ( +- 0.21% ) > 16.108302562 seconds time elapsed ( +- 0.41% ) > > If I force the function to be inline, the result is slightly worse: > > - arch_scale_cpu_capacity function [arch/arm/include/asm/topology.h] > > 16.122545216 seconds time elapsed ( +- 0.09% ) > 16.285819258 seconds time elapsed ( +- 0.35% ) > 16.157454024 seconds time elapsed ( +- 0.15% ) > > So I think we can connect the arch_scale_cpu_capacity function > [arch/arm/kernel/topology.c] to the CFS scheduler for ARCH=arm so that > people get cpu scale different to 1024 on arm big.little machines w/ > A15/A7 in case the specify clock-frequency properties in their dtb file. > > Can we still have your 'Acked-by' for this patch and 3/6 even though we > now scale weight (by frequency) and scale_freq (by cpu) instead of the > time related values (delta_w, contrib, delta)?
Yes, Please add my Acked-by
Vincent
> > Thanks, > > -- Dietmar > >> >> Regards, >> Vincent >> >>> >>> To connect the cpu invariant engine (scale_cpu_capacity() >>> [arch/arm/kernel/topology.c]) with the scheduler, something like this is >>> missing: >>> >>> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h >>> index 370f7a732900..17c6b3243196 100644 >>> --- a/arch/arm/include/asm/topology.h >>> +++ b/arch/arm/include/asm/topology.h >>> @@ -24,6 +24,10 @@ void init_cpu_topology(void); >>> void store_cpu_topology(unsigned int cpuid); >>> const struct cpumask *cpu_coregroup_mask(int cpu); >>> >>> +#define arch_scale_cpu_capacity scale_cpu_capacity >>> +struct sched_domain; >>> +extern unsigned long scale_cpu_capacity(struct sched_domain *sd, int cpu); >>> + >>> #else >>> >>> static inline void init_cpu_topology(void) { } >>> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c >>> index 08b7847bf912..907e0d2d9b82 100644 >>> --- a/arch/arm/kernel/topology.c >>> +++ b/arch/arm/kernel/topology.c >>> @@ -42,7 +42,7 @@ >>> */ >>> static DEFINE_PER_CPU(unsigned long, cpu_scale); >>> >>> -unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) >>> +unsigned long scale_cpu_capacity(struct sched_domain *sd, int cpu) >>> { >>> return per_cpu(cpu_scale, cpu); >>> } >>> @@ -166,7 +166,7 @@ static void update_cpu_capacity(unsigned int cpu) >>> set_capacity_scale(cpu, cpu_capacity(cpu) / middle_capacity); >>> >>> pr_info("CPU%u: update cpu_capacity %lu\n", >>> - cpu, arch_scale_cpu_capacity(NULL, cpu)); >>> + cpu, scale_cpu_capacity(NULL, cpu)); >>> } >>> >>> -- Dietmar >>> >>> [...] >
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