[PATCH-cgroup 3/4] cgroup/cpuset: Keep track of CPUs in isolated partitions

From: Waiman Long
Date: Fri Oct 13 2023 - 14:13:04 EST

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Add a new internal isolated_cpus mask to keep track of the CPUs that
are in isolated partitions. Expose that new cpumask as a new root-only
control file ".__DEBUG__.cpuset.cpus.isolated" when cgroup_debug command
line option is specified.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 190 +++++++++++++++++++++++++++--------------
1 file changed, 127 insertions(+), 63 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 615daaf87f1f..19c8779798fd 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -204,6 +204,11 @@ struct cpuset {
*/
static cpumask_var_t subpartitions_cpus;

+/*
+ * Exclusive CPUs in isolated partitions
+ */
+static cpumask_var_t isolated_cpus;
+
/* List of remote partition root children */
static struct list_head remote_children;

@@ -1317,6 +1322,7 @@ static void compute_effective_cpumask(struct cpumask *new_cpus,
*/
enum partition_cmd {
partcmd_enable, /* Enable partition root */
+ partcmd_enablei, /* Enable isolated partition root */
partcmd_disable, /* Disable partition root */
partcmd_update, /* Update parent's effective_cpus */
partcmd_invalidate, /* Make partition invalid */
@@ -1418,6 +1424,74 @@ static void reset_partition_data(struct cpuset *cs)
}
}

+/*
+ * partition_xcpus_newstate - Exclusive CPUs state change
+ * @old_prs: old partition_root_state
+ * @new_prs: new partition_root_state
+ * @xcpus: exclusive CPUs with state change
+ */
+static void partition_xcpus_newstate(int old_prs, int new_prs, struct cpumask *xcpus)
+{
+ WARN_ON_ONCE(old_prs == new_prs);
+ if (new_prs == PRS_ISOLATED)
+ cpumask_or(isolated_cpus, isolated_cpus, xcpus);
+ else
+ cpumask_andnot(isolated_cpus, isolated_cpus, xcpus);
+}
+
+/*
+ * partition_xcpus_add - Add new exclusive CPUs to partition
+ * @new_prs: new partition_root_state
+ * @parent: parent cpuset
+ * @xcpus: exclusive CPUs to be added
+ *
+ * Remote partition if parent == NULL
+ */
+static void partition_xcpus_add(int new_prs, struct cpuset *parent,
+ struct cpumask *xcpus)
+{
+ WARN_ON_ONCE(new_prs < 0);
+ lockdep_assert_held(&callback_lock);
+ if (!parent)
+ parent = &top_cpuset;
+
+ if (parent == &top_cpuset)
+ cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus);
+
+ if (new_prs != parent->partition_root_state)
+ partition_xcpus_newstate(parent->partition_root_state, new_prs,
+ xcpus);
+
+ cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus);
+}
+
+/*
+ * partition_xcpus_del - Remove exclusive CPUs from partition
+ * @old_prs: old partition_root_state
+ * @parent: parent cpuset
+ * @xcpus: exclusive CPUs to be removed
+ *
+ * Remote partition if parent == NULL
+ */
+static void partition_xcpus_del(int old_prs, struct cpuset *parent,
+ struct cpumask *xcpus)
+{
+ WARN_ON_ONCE(old_prs < 0);
+ lockdep_assert_held(&callback_lock);
+ if (!parent)
+ parent = &top_cpuset;
+
+ if (parent == &top_cpuset)
+ cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus);
+
+ if (old_prs != parent->partition_root_state)
+ partition_xcpus_newstate(old_prs, parent->partition_root_state,
+ xcpus);
+
+ cpumask_and(xcpus, xcpus, cpu_active_mask);
+ cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus);
+}
+
/*
* compute_effective_exclusive_cpumask - compute effective exclusive CPUs
* @cs: cpuset
@@ -1456,13 +1530,15 @@ static inline bool is_local_partition(struct cpuset *cs)
/*
* remote_partition_enable - Enable current cpuset as a remote partition root
* @cs: the cpuset to update
+ * @new_prs: new partition_root_state
* @tmp: temparary masks
* Return: 1 if successful, 0 if error
*
* Enable the current cpuset to become a remote partition root taking CPUs
* directly from the top cpuset. cpuset_mutex must be held by the caller.
*/
-static int remote_partition_enable(struct cpuset *cs, struct tmpmasks *tmp)
+static int remote_partition_enable(struct cpuset *cs, int new_prs,
+ struct tmpmasks *tmp)
{
/*
* The user must have sysadmin privilege.
@@ -1485,18 +1561,14 @@ static int remote_partition_enable(struct cpuset *cs, struct tmpmasks *tmp)
return 0;

spin_lock_irq(&callback_lock);
- cpumask_andnot(top_cpuset.effective_cpus,
- top_cpuset.effective_cpus, tmp->new_cpus);
- cpumask_or(subpartitions_cpus,
- subpartitions_cpus, tmp->new_cpus);
-
+ partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
+ list_add(&cs->remote_sibling, &remote_children);
if (cs->use_parent_ecpus) {
struct cpuset *parent = parent_cs(cs);

cs->use_parent_ecpus = false;
parent->child_ecpus_count--;
}
- list_add(&cs->remote_sibling, &remote_children);
spin_unlock_irq(&callback_lock);

/*
@@ -1524,13 +1596,8 @@ static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, subpartitions_cpus));

spin_lock_irq(&callback_lock);
- cpumask_andnot(subpartitions_cpus,
- subpartitions_cpus, tmp->new_cpus);
- cpumask_and(tmp->new_cpus,
- tmp->new_cpus, cpu_active_mask);
- cpumask_or(top_cpuset.effective_cpus,
- top_cpuset.effective_cpus, tmp->new_cpus);
list_del_init(&cs->remote_sibling);
+ partition_xcpus_del(cs->partition_root_state, NULL, tmp->new_cpus);
cs->partition_root_state = -cs->partition_root_state;
if (!cs->prs_err)
cs->prs_err = PERR_INVCPUS;
@@ -1557,6 +1624,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *newmask,
struct tmpmasks *tmp)
{
bool adding, deleting;
+ int prs = cs->partition_root_state;

if (WARN_ON_ONCE(!is_remote_partition(cs)))
return;
@@ -1580,20 +1648,10 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *newmask,
goto invalidate;

spin_lock_irq(&callback_lock);
- if (adding) {
- cpumask_or(subpartitions_cpus,
- subpartitions_cpus, tmp->addmask);
- cpumask_andnot(top_cpuset.effective_cpus,
- top_cpuset.effective_cpus, tmp->addmask);
- }
- if (deleting) {
- cpumask_andnot(subpartitions_cpus,
- subpartitions_cpus, tmp->delmask);
- cpumask_and(tmp->delmask,
- tmp->delmask, cpu_active_mask);
- cpumask_or(top_cpuset.effective_cpus,
- top_cpuset.effective_cpus, tmp->delmask);
- }
+ if (adding)
+ partition_xcpus_add(prs, NULL, tmp->addmask);
+ if (deleting)
+ partition_xcpus_del(prs, NULL, tmp->delmask);
spin_unlock_irq(&callback_lock);

/*
@@ -1676,11 +1734,11 @@ static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
* @tmp: Temporary addmask and delmask
* Return: 0 or a partition root state error code
*
- * For partcmd_enable, the cpuset is being transformed from a non-partition
- * root to a partition root. The effective_xcpus (cpus_allowed if effective_xcpus
- * not set) mask of the given cpuset will be taken away from parent's
- * effective_cpus. The function will return 0 if all the CPUs listed in
- * effective_xcpus can be granted or an error code will be returned.
+ * For partcmd_enable*, the cpuset is being transformed from a non-partition
+ * root to a partition root. The effective_xcpus (cpus_allowed if
+ * effective_xcpus not set) mask of the given cpuset will be taken away from
+ * parent's effective_cpus. The function will return 0 if all the CPUs listed
+ * in effective_xcpus can be granted or an error code will be returned.
*
* For partcmd_disable, the cpuset is being transformed from a partition
* root back to a non-partition root. Any CPUs in effective_xcpus will be
@@ -1695,7 +1753,7 @@ static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
*
* For partcmd_invalidate, the current partition will be made invalid.
*
- * The partcmd_enable and partcmd_disable commands are used by
+ * The partcmd_enable* and partcmd_disable commands are used by
* update_prstate(). An error code may be returned and the caller will check
* for error.
*
@@ -1760,7 +1818,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,

nocpu = tasks_nocpu_error(parent, cs, xcpus);

- if (cmd == partcmd_enable) {
+ if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) {
/*
* Enabling partition root is not allowed if its
* effective_xcpus is empty or doesn't overlap with
@@ -1783,6 +1841,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
cpumask_copy(tmp->delmask, xcpus);
deleting = true;
subparts_delta++;
+ new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
} else if (cmd == partcmd_disable) {
/*
* May need to add cpus to parent's effective_cpus for
@@ -1792,6 +1851,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
cpumask_and(tmp->addmask, xcpus, parent->effective_xcpus);
if (adding)
subparts_delta--;
+ new_prs = PRS_MEMBER;
} else if (newmask) {
/*
* Empty cpumask is not allowed
@@ -1940,37 +2000,24 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
* newly deleted ones will be added back to effective_cpus.
*/
spin_lock_irq(&callback_lock);
- if (adding) {
- if (parent == &top_cpuset)
- cpumask_andnot(subpartitions_cpus,
- subpartitions_cpus, tmp->addmask);
- /*
- * Some of the CPUs in effective_xcpus might have been offlined.
- */
- cpumask_or(parent->effective_cpus,
- parent->effective_cpus, tmp->addmask);
- cpumask_and(parent->effective_cpus,
- parent->effective_cpus, cpu_active_mask);
- }
- if (deleting) {
- if (parent == &top_cpuset)
- cpumask_or(subpartitions_cpus,
- subpartitions_cpus, tmp->delmask);
- cpumask_andnot(parent->effective_cpus,
- parent->effective_cpus, tmp->delmask);
- }
-
- if (is_partition_valid(parent)) {
- parent->nr_subparts += subparts_delta;
- WARN_ON_ONCE(parent->nr_subparts < 0);
- }
-
if (old_prs != new_prs) {
cs->partition_root_state = new_prs;
if (new_prs <= 0)
cs->nr_subparts = 0;
}
+ /*
+ * Adding to parent's effective_cpus means deletion CPUs from cs
+ * and vice versa.
+ */
+ if (adding)
+ partition_xcpus_del(old_prs, parent, tmp->addmask);
+ if (deleting)
+ partition_xcpus_add(new_prs, parent, tmp->delmask);

+ if (is_partition_valid(parent)) {
+ parent->nr_subparts += subparts_delta;
+ WARN_ON_ONCE(parent->nr_subparts < 0);
+ }
spin_unlock_irq(&callback_lock);

if ((old_prs != new_prs) && (cmd == partcmd_update))
@@ -2948,6 +2995,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
int err = PERR_NONE, old_prs = cs->partition_root_state;
struct cpuset *parent = parent_cs(cs);
struct tmpmasks tmpmask;
+ bool new_xcpus_state = false;

if (old_prs == new_prs)
return 0;
@@ -2977,6 +3025,9 @@ static int update_prstate(struct cpuset *cs, int new_prs)
goto out;

if (!old_prs) {
+ enum partition_cmd cmd = (new_prs == PRS_ROOT)
+ ? partcmd_enable : partcmd_enablei;
+
/*
* cpus_allowed cannot be empty.
*/
@@ -2985,19 +3036,18 @@ static int update_prstate(struct cpuset *cs, int new_prs)
goto out;
}

- err = update_parent_effective_cpumask(cs, partcmd_enable,
- NULL, &tmpmask);
+ err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
/*
* If an attempt to become local partition root fails,
* try to become a remote partition root instead.
*/
- if (err && remote_partition_enable(cs, &tmpmask))
+ if (err && remote_partition_enable(cs, new_prs, &tmpmask))
err = 0;
} else if (old_prs && new_prs) {
/*
* A change in load balance state only, no change in cpumasks.
*/
- ;
+ new_xcpus_state = true;
} else {
/*
* Switching back to member is always allowed even if it
@@ -3029,6 +3079,8 @@ static int update_prstate(struct cpuset *cs, int new_prs)
WRITE_ONCE(cs->prs_err, err);
if (!is_partition_valid(cs))
reset_partition_data(cs);
+ else if (new_xcpus_state)
+ partition_xcpus_newstate(old_prs, new_prs, cs->effective_xcpus);
spin_unlock_irq(&callback_lock);

/* Force update if switching back to member */
@@ -3386,6 +3438,7 @@ typedef enum {
FILE_SUBPARTS_CPULIST,
FILE_EXCLUSIVE_CPULIST,
FILE_EFFECTIVE_XCPULIST,
+ FILE_ISOLATED_CPULIST,
FILE_CPU_EXCLUSIVE,
FILE_MEM_EXCLUSIVE,
FILE_MEM_HARDWALL,
@@ -3582,6 +3635,9 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
case FILE_SUBPARTS_CPULIST:
seq_printf(sf, "%*pbl\n", cpumask_pr_args(subpartitions_cpus));
break;
+ case FILE_ISOLATED_CPULIST:
+ seq_printf(sf, "%*pbl\n", cpumask_pr_args(isolated_cpus));
+ break;
default:
ret = -EINVAL;
}
@@ -3875,6 +3931,13 @@ static struct cftype dfl_files[] = {
.flags = CFTYPE_ONLY_ON_ROOT | CFTYPE_DEBUG,
},

+ {
+ .name = "cpus.isolated",
+ .seq_show = cpuset_common_seq_show,
+ .private = FILE_ISOLATED_CPULIST,
+ .flags = CFTYPE_ONLY_ON_ROOT | CFTYPE_DEBUG,
+ },
+
{ } /* terminate */
};

@@ -4194,6 +4257,7 @@ int __init cpuset_init(void)
BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_xcpus, GFP_KERNEL));
BUG_ON(!alloc_cpumask_var(&top_cpuset.exclusive_cpus, GFP_KERNEL));
BUG_ON(!zalloc_cpumask_var(&subpartitions_cpus, GFP_KERNEL));
+ BUG_ON(!zalloc_cpumask_var(&isolated_cpus, GFP_KERNEL));

cpumask_setall(top_cpuset.cpus_allowed);
nodes_setall(top_cpuset.mems_allowed);
--
2.39.3

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