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sched: convert struct sched_group/sched_domain cpumask_ts to variable…
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Impact: (future) size reduction for large NR_CPUS.

We move the 'cpumask' member of sched_group to the end, so when we
kmalloc it we can do a minimal allocation: saves space for small
nr_cpu_ids but big CONFIG_NR_CPUS.  Similar trick for 'span' in
sched_domain.

This isn't quite as good as converting to a cpumask_var_t, as some
sched_groups are actually static, but it's safer: we don't have to
figure out where to call alloc_cpumask_var/free_cpumask_var.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Rusty Russell authored and Ingo Molnar committed Nov 24, 2008
1 parent 758b2cd commit 6c99e9a
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Showing 2 changed files with 48 additions and 28 deletions.
11 changes: 7 additions & 4 deletions include/linux/sched.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -771,7 +771,6 @@ enum cpu_idle_type {

struct sched_group {
struct sched_group *next; /* Must be a circular list */
cpumask_t cpumask;

/*
* CPU power of this group, SCHED_LOAD_SCALE being max power for a
Expand All @@ -784,11 +783,13 @@ struct sched_group {
* (see include/linux/reciprocal_div.h)
*/
u32 reciprocal_cpu_power;

unsigned long cpumask[];
};

static inline struct cpumask *sched_group_cpus(struct sched_group *sg)
{
return &sg->cpumask;
return to_cpumask(sg->cpumask);
}

enum sched_domain_level {
Expand All @@ -814,7 +815,6 @@ struct sched_domain {
struct sched_domain *parent; /* top domain must be null terminated */
struct sched_domain *child; /* bottom domain must be null terminated */
struct sched_group *groups; /* the balancing groups of the domain */
cpumask_t span; /* span of all CPUs in this domain */
unsigned long min_interval; /* Minimum balance interval ms */
unsigned long max_interval; /* Maximum balance interval ms */
unsigned int busy_factor; /* less balancing by factor if busy */
Expand Down Expand Up @@ -869,11 +869,14 @@ struct sched_domain {
#ifdef CONFIG_SCHED_DEBUG
char *name;
#endif

/* span of all CPUs in this domain */
unsigned long span[];
};

static inline struct cpumask *sched_domain_span(struct sched_domain *sd)
{
return &sd->span;
return to_cpumask(sd->span);
}

extern void partition_sched_domains(int ndoms_new, cpumask_t *doms_new,
Expand Down
65 changes: 41 additions & 24 deletions kernel/sched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7005,19 +7005,34 @@ static void sched_domain_node_span(int node, cpumask_t *span)

int sched_smt_power_savings = 0, sched_mc_power_savings = 0;

/*
* The cpus mask in sched_group and sched_domain hangs off the end.
* FIXME: use cpumask_var_t or dynamic percpu alloc to avoid wasting space
* for nr_cpu_ids < CONFIG_NR_CPUS.
*/
struct static_sched_group {
struct sched_group sg;
DECLARE_BITMAP(cpus, CONFIG_NR_CPUS);
};

struct static_sched_domain {
struct sched_domain sd;
DECLARE_BITMAP(span, CONFIG_NR_CPUS);
};

/*
* SMT sched-domains:
*/
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_cpus);
static DEFINE_PER_CPU(struct static_sched_domain, cpu_domains);
static DEFINE_PER_CPU(struct static_sched_group, sched_group_cpus);

static int
cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
cpumask_t *unused)
{
if (sg)
*sg = &per_cpu(sched_group_cpus, cpu);
*sg = &per_cpu(sched_group_cpus, cpu).sg;
return cpu;
}
#endif /* CONFIG_SCHED_SMT */
Expand All @@ -7026,8 +7041,8 @@ cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
* multi-core sched-domains:
*/
#ifdef CONFIG_SCHED_MC
static DEFINE_PER_CPU(struct sched_domain, core_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_core);
static DEFINE_PER_CPU(struct static_sched_domain, core_domains);
static DEFINE_PER_CPU(struct static_sched_group, sched_group_core);
#endif /* CONFIG_SCHED_MC */

#if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
Expand All @@ -7041,7 +7056,7 @@ cpu_to_core_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
cpus_and(*mask, *mask, *cpu_map);
group = first_cpu(*mask);
if (sg)
*sg = &per_cpu(sched_group_core, group);
*sg = &per_cpu(sched_group_core, group).sg;
return group;
}
#elif defined(CONFIG_SCHED_MC)
Expand All @@ -7050,13 +7065,13 @@ cpu_to_core_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
cpumask_t *unused)
{
if (sg)
*sg = &per_cpu(sched_group_core, cpu);
*sg = &per_cpu(sched_group_core, cpu).sg;
return cpu;
}
#endif

static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_phys);
static DEFINE_PER_CPU(struct static_sched_domain, phys_domains);
static DEFINE_PER_CPU(struct static_sched_group, sched_group_phys);

static int
cpu_to_phys_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
Expand All @@ -7075,7 +7090,7 @@ cpu_to_phys_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
group = cpu;
#endif
if (sg)
*sg = &per_cpu(sched_group_phys, group);
*sg = &per_cpu(sched_group_phys, group).sg;
return group;
}

Expand All @@ -7089,7 +7104,7 @@ static DEFINE_PER_CPU(struct sched_domain, node_domains);
static struct sched_group ***sched_group_nodes_bycpu;

static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_allnodes);
static DEFINE_PER_CPU(struct static_sched_group, sched_group_allnodes);

static int cpu_to_allnodes_group(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg, cpumask_t *nodemask)
Expand All @@ -7101,7 +7116,7 @@ static int cpu_to_allnodes_group(int cpu, const cpumask_t *cpu_map,
group = first_cpu(*nodemask);

if (sg)
*sg = &per_cpu(sched_group_allnodes, group);
*sg = &per_cpu(sched_group_allnodes, group).sg;
return group;
}

Expand All @@ -7116,7 +7131,7 @@ static void init_numa_sched_groups_power(struct sched_group *group_head)
for_each_cpu(j, sched_group_cpus(sg)) {
struct sched_domain *sd;

sd = &per_cpu(phys_domains, j);
sd = &per_cpu(phys_domains, j).sd;
if (j != cpumask_first(sched_group_cpus(sd->groups))) {
/*
* Only add "power" once for each
Expand Down Expand Up @@ -7385,7 +7400,7 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
#endif

p = sd;
sd = &per_cpu(phys_domains, i);
sd = &per_cpu(phys_domains, i).sd;
SD_INIT(sd, CPU);
set_domain_attribute(sd, attr);
cpumask_copy(sched_domain_span(sd), nodemask);
Expand All @@ -7396,7 +7411,7 @@ static int __build_sched_domains(const cpumask_t *cpu_map,

#ifdef CONFIG_SCHED_MC
p = sd;
sd = &per_cpu(core_domains, i);
sd = &per_cpu(core_domains, i).sd;
SD_INIT(sd, MC);
set_domain_attribute(sd, attr);
*sched_domain_span(sd) = cpu_coregroup_map(i);
Expand All @@ -7409,7 +7424,7 @@ static int __build_sched_domains(const cpumask_t *cpu_map,

#ifdef CONFIG_SCHED_SMT
p = sd;
sd = &per_cpu(cpu_domains, i);
sd = &per_cpu(cpu_domains, i).sd;
SD_INIT(sd, SIBLING);
set_domain_attribute(sd, attr);
cpumask_and(sched_domain_span(sd),
Expand Down Expand Up @@ -7485,7 +7500,8 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
sched_domain_node_span(i, domainspan);
cpus_and(*domainspan, *domainspan, *cpu_map);

sg = kmalloc_node(sizeof(struct sched_group), GFP_KERNEL, i);
sg = kmalloc_node(sizeof(struct sched_group) + cpumask_size(),
GFP_KERNEL, i);
if (!sg) {
printk(KERN_WARNING "Can not alloc domain group for "
"node %d\n", i);
Expand Down Expand Up @@ -7518,7 +7534,8 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
if (cpus_empty(*tmpmask))
continue;

sg = kmalloc_node(sizeof(struct sched_group),
sg = kmalloc_node(sizeof(struct sched_group) +
cpumask_size(),
GFP_KERNEL, i);
if (!sg) {
printk(KERN_WARNING
Expand All @@ -7538,21 +7555,21 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
/* Calculate CPU power for physical packages and nodes */
#ifdef CONFIG_SCHED_SMT
for_each_cpu(i, cpu_map) {
struct sched_domain *sd = &per_cpu(cpu_domains, i);
struct sched_domain *sd = &per_cpu(cpu_domains, i).sd;

init_sched_groups_power(i, sd);
}
#endif
#ifdef CONFIG_SCHED_MC
for_each_cpu(i, cpu_map) {
struct sched_domain *sd = &per_cpu(core_domains, i);
struct sched_domain *sd = &per_cpu(core_domains, i).sd;

init_sched_groups_power(i, sd);
}
#endif

for_each_cpu(i, cpu_map) {
struct sched_domain *sd = &per_cpu(phys_domains, i);
struct sched_domain *sd = &per_cpu(phys_domains, i).sd;

init_sched_groups_power(i, sd);
}
Expand All @@ -7574,11 +7591,11 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
for_each_cpu(i, cpu_map) {
struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
sd = &per_cpu(cpu_domains, i).sd;
#elif defined(CONFIG_SCHED_MC)
sd = &per_cpu(core_domains, i);
sd = &per_cpu(core_domains, i).sd;
#else
sd = &per_cpu(phys_domains, i);
sd = &per_cpu(phys_domains, i).sd;
#endif
cpu_attach_domain(sd, rd, i);
}
Expand Down

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