[RFC PATCH] Dynamic sched domains (v0.5)

Dinakar Guniguntala
2005-05-01T18:59:28Z

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Ok, Here is the minimal patchset that I had promised after the
last discussion.

What it does have
o The current patch enhances the meaning of exclusive cpusets by
attaching them (exclusive cpusets) to sched domains
o It does _not_ require any additional cpumask_t variable. It
just parses the cpus_allowed of the parent/sibling/children
cpusets for manipulating sched domains
o All existing operations on non-/exclusive cpusets are preserved as-is.
o The sched code has been modified to bring it upto 2.6.12-rc2-mm3

Usage
o On setting the cpu_exclusive flag of a cpuset X, it creates two
sched domains
a. One, All cpus from X's parent cpuset that dont belong to any
exclusive sibling cpuset of X
b. Two, All cpus in X's cpus_allowed
o On adding/deleting cpus to/from a exclusive cpuset X that has exclusive
children, it creates two sched domains
a. One, All cpus from X's parent cpuset that dont belong to any
exclusive sibling cpuset of X
b. Two, All cpus in X's cpus_allowed, after taking away any cpus that
belong to exclusive child cpusets of X
o On unsetting the cpu_exclusive flag of cpuset X or rmdir X, it creates a
single sched domain, containing all cpus from X' parent cpuset that
dont belong to any exclusive sibling of X and the cpus of X
o It does _not_ modify the cpus_allowed variable of the parent as in the
previous version. It relies on user space to move tasks to proper
cpusets for complete isolation/exclusion
o See function update_cpu_domains for more details

What it does not have
o It is still short on documentation
o Does not have hotplug support as yet
o Supports only x86 as of now
o No thoughts on "memory domains" (Though I am not sure, who
would use such a thing and what exactly are the requirements)

Here is the increase in binary sizes for different values of CONFIG_NR_CPUS
(32 and 255)

kernel/cpuset.o.orig-32 16728
kernel/cpuset.o-v0.5-32 17176 (~2.7% increase)

kernel/cpuset.o.orig-255 17916
kernel/cpuset.o-v0.5-255 19120 (~6.7% increase)

The code changes are also minimal

include/linux/init.h | 2
include/linux/sched.h | 1
kernel/cpuset.c | 73 +++++++++++++++++++++++++++------
kernel/sched.c | 109 +++++++++++++++++++++++++++++++++-----------------
4 files changed, 134 insertions(+), 51 deletions(-)

-Dinakar

[-- Attachment #2: dyn-sd-v0.5-1.patch --]
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diff -Naurp linux-2.6.12-rc2.orig/include/linux/init.h linux-2.6.12-rc2/include/linux/init.h
--- linux-2.6.12-rc2.orig/include/linux/init.h 2005-04-04 22:07:52.000000000 +0530
+++ linux-2.6.12-rc2/include/linux/init.h 2005-05-01 22:07:56.000000000 +0530
@@ -217,7 +217,7 @@ void __init parse_early_param(void);
#define __initdata_or_module __initdata
#endif /*CONFIG_MODULES*/

-#ifdef CONFIG_HOTPLUG
+#if defined(CONFIG_HOTPLUG) || defined(CONFIG_CPUSETS)
#define __devinit
#define __devinitdata
#define __devexit
diff -Naurp linux-2.6.12-rc2.orig/include/linux/sched.h linux-2.6.12-rc2/include/linux/sched.h
--- linux-2.6.12-rc2.orig/include/linux/sched.h 2005-04-28 18:24:11.000000000 +0530
+++ linux-2.6.12-rc2/include/linux/sched.h 2005-05-01 22:07:35.000000000 +0530
@@ -155,6 +155,7 @@ typedef struct task_struct task_t;
extern void sched_init(void);
extern void sched_init_smp(void);
extern void init_idle(task_t *idle, int cpu);
+extern void rebuild_sched_domains(cpumask_t span1, cpumask_t span2);

extern cpumask_t nohz_cpu_mask;

diff -Naurp linux-2.6.12-rc2.orig/kernel/sched.c linux-2.6.12-rc2/kernel/sched.c
--- linux-2.6.12-rc2.orig/kernel/sched.c 2005-04-28 18:24:11.000000000 +0530
+++ linux-2.6.12-rc2/kernel/sched.c 2005-05-01 22:06:55.000000000 +0530
@@ -4526,7 +4526,7 @@ int __init migration_init(void)
#endif

#ifdef CONFIG_SMP
-#define SCHED_DOMAIN_DEBUG
+#undef SCHED_DOMAIN_DEBUG
#ifdef SCHED_DOMAIN_DEBUG
static void sched_domain_debug(struct sched_domain *sd, int cpu)
{
@@ -4934,40 +4934,50 @@ static void check_sibling_maps(void)
}
#endif

-/*
- * Set up scheduler domains and groups. Callers must hold the hotplug lock.
- */
-static void __devinit arch_init_sched_domains(void)
+static inline void detach_domains(cpumask_t cpu_map)
{
int i;
- cpumask_t cpu_default_map;

-#if defined(CONFIG_SCHED_SMT) && defined(CONFIG_NUMA)
- check_sibling_maps();
+ for_each_cpu_mask(i, cpu_map)
+ cpu_attach_domain(NULL, i);
+ synchronize_kernel();
+}
+
+static inline void attach_domains(cpumask_t cpu_map)
+{
+ int i;
+
+ /* Attach the domains */
+ for_each_cpu_mask(i, cpu_map) {
+ struct sched_domain *sd;
+#ifdef CONFIG_SCHED_SMT
+ sd = &per_cpu(cpu_domains, i);
+#else
+ sd = &per_cpu(phys_domains, i);
#endif
- /*
- * Setup mask for cpus without special case scheduling requirements.
- * For now this just excludes isolated cpus, but could be used to
- * exclude other special cases in the future.
- */
- cpus_complement(cpu_default_map, cpu_isolated_map);
- cpus_and(cpu_default_map, cpu_default_map, cpu_online_map);
+ cpu_attach_domain(sd, i);
+ }
+}
+
+static void build_sched_domains(cpumask_t cpu_map)
+{
+ int i;

/*
- * Set up domains. Isolated domains just stay on the NULL domain.
+ * Set up domains as specified by the cpu_map.
*/
- for_each_cpu_mask(i, cpu_default_map) {
+ for_each_cpu_mask(i, cpu_map) {
int group;
struct sched_domain *sd = NULL, *p;
cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));

- cpus_and(nodemask, nodemask, cpu_default_map);
+ cpus_and(nodemask, nodemask, cpu_map);

#ifdef CONFIG_NUMA
sd = &per_cpu(node_domains, i);
group = cpu_to_node_group(i);
*sd = SD_NODE_INIT;
- sd->span = cpu_default_map;
+ sd->span = cpu_map;
sd->groups = &sched_group_nodes[group];
#endif

@@ -4985,7 +4995,7 @@ static void __devinit arch_init_sched_do
group = cpu_to_cpu_group(i);
*sd = SD_SIBLING_INIT;
sd->span = cpu_sibling_map[i];
- cpus_and(sd->span, sd->span, cpu_default_map);
+ cpus_and(sd->span, sd->span, cpu_map);
sd->parent = p;
sd->groups = &sched_group_cpus[group];
#endif
@@ -4995,7 +5005,7 @@ static void __devinit arch_init_sched_do
/* Set up CPU (sibling) groups */
for_each_online_cpu(i) {
cpumask_t this_sibling_map = cpu_sibling_map[i];
- cpus_and(this_sibling_map, this_sibling_map, cpu_default_map);
+ cpus_and(this_sibling_map, this_sibling_map, cpu_map);
if (i != first_cpu(this_sibling_map))
continue;

@@ -5008,7 +5018,7 @@ static void __devinit arch_init_sched_do
for (i = 0; i < MAX_NUMNODES; i++) {
cpumask_t nodemask = node_to_cpumask(i);

- cpus_and(nodemask, nodemask, cpu_default_map);
+ cpus_and(nodemask, nodemask, cpu_map);
if (cpus_empty(nodemask))
continue;

@@ -5018,12 +5028,12 @@ static void __devinit arch_init_sched_do

#ifdef CONFIG_NUMA
/* Set up node groups */
- init_sched_build_groups(sched_group_nodes, cpu_default_map,
+ init_sched_build_groups(sched_group_nodes, cpu_map,
&cpu_to_node_group);
#endif

/* Calculate CPU power for physical packages and nodes */
- for_each_cpu_mask(i, cpu_default_map) {
+ for_each_cpu_mask(i, cpu_map) {
int power;
struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
@@ -5045,17 +5055,46 @@ static void __devinit arch_init_sched_do
}
#endif
}
+}

- /* Attach the domains */
- for_each_online_cpu(i) {
- struct sched_domain *sd;
-#ifdef CONFIG_SCHED_SMT
- sd = &per_cpu(cpu_domains, i);
-#else
- sd = &per_cpu(phys_domains, i);
+void rebuild_sched_domains(cpumask_t span1, cpumask_t span2)
+{
+ cpumask_t change_map;
+
+ cpus_or(change_map, span1, span2);
+
+ preempt_disable();
+ detach_domains(change_map);
+
+ if (!cpus_empty(span1))
+ build_sched_domains(span1);
+ if (!cpus_empty(span2))
+ build_sched_domains(span2);
+
+ attach_domains(change_map);
+ preempt_enable();
+}
+
+/*
+ * Set up scheduler domains and groups. Callers must hold the hotplug lock.
+ */
+static void __devinit arch_init_sched_domains(void)
+{
+ cpumask_t cpu_default_map;
+
+#if defined(CONFIG_SCHED_SMT) && defined(CONFIG_NUMA)
+ check_sibling_maps();
#endif
- cpu_attach_domain(sd, i);
- }
+ /*
+ * Setup mask for cpus without special case scheduling requirements.
+ * For now this just excludes isolated cpus, but could be used to
+ * exclude other special cases in the future.
+ */
+ cpus_complement(cpu_default_map, cpu_isolated_map);
+ cpus_and(cpu_default_map, cpu_default_map, cpu_online_map);
+
+ build_sched_domains(cpu_default_map);
+ attach_domains(cpu_default_map);
}

#ifdef CONFIG_HOTPLUG_CPU
@@ -5082,9 +5121,7 @@ static int update_sched_domains(struct n
switch (action) {
case CPU_UP_PREPARE:
case CPU_DOWN_PREPARE:
- for_each_online_cpu(i)
- cpu_attach_domain(NULL, i);
- synchronize_kernel();
+ detach_domains(cpu_online_map);
arch_destroy_sched_domains();
return NOTIFY_OK;

[-- Attachment #3: dyn-sd-v0.5-2.patch --]
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diff -Naurp linux-2.6.12-rc2.orig/kernel/cpuset.c linux-2.6.12-rc2/kernel/cpuset.c
--- linux-2.6.12-rc2.orig/kernel/cpuset.c 2005-04-28 18:24:11.000000000 +0530
+++ linux-2.6.12-rc2/kernel/cpuset.c 2005-05-01 22:15:06.000000000 +0530
@@ -602,12 +602,48 @@ static int validate_change(const struct
return 0;
}

+static void update_cpu_domains(struct cpuset *cur)
+{
+ struct cpuset *c, *par = cur->parent;
+ cpumask_t span1, span2;
+
+ if (par == NULL || cpus_empty(cur->cpus_allowed))
+ return;
+
+ /* Get all non-exclusive cpus from parent domain */
+ span1 = par->cpus_allowed;
+ list_for_each_entry(c, &par->children, sibling) {
+ if (is_cpu_exclusive(c))
+ cpus_andnot(span1, span1, c->cpus_allowed);
+ }
+ if (is_removed(cur) || !is_cpu_exclusive(cur)) {
+ cpus_or(span1, span1, cur->cpus_allowed);
+ if (cpus_equal(span1, cur->cpus_allowed))
+ return;
+ span2 = CPU_MASK_NONE;
+ }
+ else {
+ if (cpus_empty(span1))
+ return;
+ span2 = cur->cpus_allowed;
+ /* If current cpuset has exclusive children, exclude from domain */
+ list_for_each_entry(c, &cur->children, sibling) {
+ if (is_cpu_exclusive(c))
+ cpus_andnot(span2, span2, c->cpus_allowed);
+ }
+ }
+
+ lock_cpu_hotplug();
+ rebuild_sched_domains(span1, span2);
+ unlock_cpu_hotplug();
+}
+
static int update_cpumask(struct cpuset *cs, char *buf)
{
- struct cpuset trialcs;
+ struct cpuset trialcs, oldcs;
int retval;

- trialcs = *cs;
+ trialcs = oldcs = *cs;
retval = cpulist_parse(buf, trialcs.cpus_allowed);
if (retval < 0)
return retval;
@@ -615,9 +651,13 @@ static int update_cpumask(struct cpuset
if (cpus_empty(trialcs.cpus_allowed))
return -ENOSPC;
retval = validate_change(cs, &trialcs);
- if (retval == 0)
- cs->cpus_allowed = trialcs.cpus_allowed;
- return retval;
+ if (retval < 0)
+ return retval;
+ cs->cpus_allowed = trialcs.cpus_allowed;
+ if (is_cpu_exclusive(cs) &&
+ (!cpus_equal(cs->cpus_allowed, oldcs.cpus_allowed)))
+ update_cpu_domains(cs);
+ return 0;
}

static int update_nodemask(struct cpuset *cs, char *buf)
@@ -652,25 +692,28 @@ static int update_nodemask(struct cpuset
static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
{
int turning_on;
- struct cpuset trialcs;
+ struct cpuset trialcs, oldcs;
int err;

turning_on = (simple_strtoul(buf, NULL, 10) != 0);

- trialcs = *cs;
+ trialcs = oldcs = *cs;
if (turning_on)
set_bit(bit, &trialcs.flags);
else
clear_bit(bit, &trialcs.flags);

err = validate_change(cs, &trialcs);
- if (err == 0) {
- if (turning_on)
- set_bit(bit, &cs->flags);
- else
- clear_bit(bit, &cs->flags);
- }
- return err;
+ if (err < 0)
+ return err;
+ if (turning_on)
+ set_bit(bit, &cs->flags);
+ else
+ clear_bit(bit, &cs->flags);
+
+ if (is_cpu_exclusive(cs) != is_cpu_exclusive(&oldcs))
+ update_cpu_domains(cs);
+ return 0;
}

static int attach_task(struct cpuset *cs, char *buf)
@@ -1319,6 +1362,8 @@ static int cpuset_rmdir(struct inode *un
spin_lock(&cs->dentry->d_lock);
parent = cs->parent;
set_bit(CS_REMOVED, &cs->flags);
+ if (is_cpu_exclusive(cs))
+ update_cpu_domains(cs);
list_del(&cs->sibling); /* delete my sibling from parent->children */
if (list_empty(&parent->children))
check_for_release(parent);