Messages in this thread | | | From | Vincent Guittot <> | Date | Tue, 17 Oct 2017 14:28:01 +0200 | Subject | Re: [PATCH v2 1/1] arm: topology: remove cpu_efficiency |
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Hi Dietmar,
On 12 October 2017 at 16:00, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > Remove the 'cpu_efficiency/clock-frequency dt property' based solution > to set cpu capacity which was only working for Cortex-A15/A7 arm > big.LITTLE systems. > > I.e. the 'capacity-dmips-mhz' based solution is now the only one. It is > shared between arm and arm64 and works for every big.LITTLE system no > matter which core types it consists of. > > Cc: Russell King <linux@arm.linux.org.uk> > Cc: Vincent Guittot <vincent.guittot@linaro.org> > Cc: Juri Lelli <juri.lelli@gmail.com> > Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > --- > arch/arm/kernel/topology.c | 132 ++------------------------------------------- > 1 file changed, 4 insertions(+), 128 deletions(-) > > diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c > index 24ac3cab411d..15cc131ae387 100644 > --- a/arch/arm/kernel/topology.c > +++ b/arch/arm/kernel/topology.c > @@ -30,69 +30,11 @@ > #include <asm/cputype.h> > #include <asm/topology.h> > > -/* > - * cpu capacity scale management > - */ > - > -/* > - * cpu capacity table > - * This per cpu data structure describes the relative capacity of each core. > - * On a heteregenous system, cores don't have the same computation capacity > - * and we reflect that difference in the cpu_capacity field so the scheduler > - * can take this difference into account during load balance. A per cpu > - * structure is preferred because each CPU updates its own cpu_capacity field > - * during the load balance except for idle cores. One idle core is selected > - * to run the rebalance_domains for all idle cores and the cpu_capacity can be > - * updated during this sequence. > - */ > - > #ifdef CONFIG_OF > -struct cpu_efficiency { > - const char *compatible; > - unsigned long efficiency; > -}; > - > -/* > - * Table of relative efficiency of each processors > - * The efficiency value must fit in 20bit and the final > - * cpu_scale value must be in the range > - * 0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2 > - * in order to return at most 1 when DIV_ROUND_CLOSEST > - * is used to compute the capacity of a CPU. > - * Processors that are not defined in the table, > - * use the default SCHED_CAPACITY_SCALE value for cpu_scale. > - */ > -static const struct cpu_efficiency table_efficiency[] = { > - {"arm,cortex-a15", 3891}, > - {"arm,cortex-a7", 2048}, > - {NULL, }, > -}; > - > -static unsigned long *__cpu_capacity; > -#define cpu_capacity(cpu) __cpu_capacity[cpu] > - > -static unsigned long middle_capacity = 1; > -static bool cap_from_dt = true; > - > -/* > - * Iterate all CPUs' descriptor in DT and compute the efficiency > - * (as per table_efficiency). Also calculate a middle efficiency > - * as close as possible to (max{eff_i} - min{eff_i}) / 2 > - * This is later used to scale the cpu_capacity field such that an > - * 'average' CPU is of middle capacity. Also see the comments near > - * table_efficiency[] and update_cpu_capacity(). > - */ > static void __init parse_dt_topology(void) > { > - const struct cpu_efficiency *cpu_eff; > - struct device_node *cn = NULL; > - unsigned long min_capacity = ULONG_MAX; > - unsigned long max_capacity = 0; > - unsigned long capacity = 0; > - int cpu = 0; > - > - __cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity), > - GFP_NOWAIT); > + struct device_node *cn; > + int cpu; > > cn = of_find_node_by_path("/cpus"); > if (!cn) { > @@ -101,9 +43,6 @@ static void __init parse_dt_topology(void) > } > > for_each_possible_cpu(cpu) { > - const u32 *rate; > - int len; > - > /* too early to use cpu->of_node */ > cn = of_get_cpu_node(cpu, NULL); > if (!cn) { > @@ -111,76 +50,15 @@ static void __init parse_dt_topology(void) > continue; > } > > - if (topology_parse_cpu_capacity(cn, cpu)) { > + if (topology_parse_cpu_capacity(cn, cpu)) > of_node_put(cn);
We should call the of_node_put unconditionally to balance the of_get_cpu_node, isn't it ? Note that this problem is also present without your change
> - continue; > - } > - > - cap_from_dt = false; > - > - for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++) > - if (of_device_is_compatible(cn, cpu_eff->compatible)) > - break; > - > - if (cpu_eff->compatible == NULL) > - continue; > - > - rate = of_get_property(cn, "clock-frequency", &len); > - if (!rate || len != 4) { > - pr_err("%pOF missing clock-frequency property\n", cn); > - continue; > - } > - > - capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency; > - > - /* Save min capacity of the system */ > - if (capacity < min_capacity) > - min_capacity = capacity; > - > - /* Save max capacity of the system */ > - if (capacity > max_capacity) > - max_capacity = capacity; > - > - cpu_capacity(cpu) = capacity; > } > > - /* If min and max capacities are equals, we bypass the update of the > - * cpu_scale because all CPUs have the same capacity. Otherwise, we > - * compute a middle_capacity factor that will ensure that the capacity > - * of an 'average' CPU of the system will be as close as possible to > - * SCHED_CAPACITY_SCALE, which is the default value, but with the > - * constraint explained near table_efficiency[]. > - */ > - if (4*max_capacity < (3*(max_capacity + min_capacity))) > - middle_capacity = (min_capacity + max_capacity) > - >> (SCHED_CAPACITY_SHIFT+1); > - else > - middle_capacity = ((max_capacity / 3) > - >> (SCHED_CAPACITY_SHIFT-1)) + 1; > - > - if (cap_from_dt) > - topology_normalize_cpu_scale(); > -} > - > -/* > - * Look for a customed capacity of a CPU in the cpu_capacity table during the > - * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the > - * function returns directly for SMP system. > - */ > -static void update_cpu_capacity(unsigned int cpu) > -{ > - if (!cpu_capacity(cpu) || cap_from_dt) > - return; > - > - topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity); > - > - pr_info("CPU%u: update cpu_capacity %lu\n", > - cpu, topology_get_cpu_scale(NULL, cpu)); > + topology_normalize_cpu_scale(); > } > > #else > static inline void parse_dt_topology(void) {} > -static inline void update_cpu_capacity(unsigned int cpuid) {} > #endif > > /* > @@ -276,8 +154,6 @@ void store_cpu_topology(unsigned int cpuid) > > update_siblings_masks(cpuid); > > - update_cpu_capacity(cpuid); > - > pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n", > cpuid, cpu_topology[cpuid].thread_id, > cpu_topology[cpuid].core_id, > -- > 2.11.0 >
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