Paul Jackson wrote:
From: Paul Jackson <[email protected]>
Remove the cpuset hooks that defined sched domains depending on the
setting of the 'cpu_exclusive' flag.
Before we chuck the baby out...
The cpu_exclusive flag can only be set on a child if it is set on
the parent.
This made that flag painfully unsuitable for use as a flag defining
a partitioning of a system.
Sigh, it isn't. That's simply how cpusets tried to use it.
It was entirely unobvious to a cpuset user what partitioning of sched
domains they would be causing when they set that one cpu_exclusive bit
on one cpuset, because it depended on what CPUs were in the remainder
of that cpusets siblings and child cpusets, after subtracting out
other cpu_exclusive cpusets.
As far as a user is concerned, the cpusets is the interface. domain
partitioning is an implementation detail that just happens to make
it work better in some cases.
Furthermore, there was no way on production systems to query the
result.
You shouldn't need to, assuming cpusets doesn't mess it up.
Here is an untested patch. Apparently takes care of CPU hotplug too.
--
SUSE Labs, Novell Inc.
Fix sched-domains partitioning by cpusets. Walk the whole cpusets tree after
something interesting changes, and recreate all partitions.
Index: linux-2.6/kernel/cpuset.c
===================================================================
--- linux-2.6.orig/kernel/cpuset.c 2006-10-19 19:26:54.000000000 +1000
+++ linux-2.6/kernel/cpuset.c 2006-10-19 20:21:29.000000000 +1000
@@ -751,6 +751,24 @@ static int validate_change(const struct
return 0;
}
+static void update_cpu_domains_children(struct cpuset *par,
+ cpumask_t *non_partitioned)
+{
+ struct cpuset *c;
+
+ list_for_each_entry(c, &par->children, sibling) {
+ if (cpus_empty(c->cpus_allowed))
+ continue;
+ if (is_cpu_exclusive(c)) {
+ if (!partition_sched_domains(&c->cpus_allowed)) {
+ cpus_andnot(*non_partitioned,
+ *non_partitioned, c->cpus_allowed);
+ }
+ } else
+ update_cpu_domains_children(c, non_partitioned);
+ }
+}
+
/*
* For a given cpuset cur, partition the system as follows
* a. All cpus in the parent cpuset's cpus_allowed that are not part of any
@@ -760,53 +778,38 @@ static int validate_change(const struct
* Build these two partitions by calling partition_sched_domains
*
* Call with manage_mutex held. May nest a call to the
- * lock_cpu_hotplug()/unlock_cpu_hotplug() pair.
- * Must not be called holding callback_mutex, because we must
- * not call lock_cpu_hotplug() while holding callback_mutex.
+ * lock_cpu_hotplug()/unlock_cpu_hotplug() pair. Must not be called holding
+ * callback_mutex, because we must not call lock_cpu_hotplug() while holding
+ * callback_mutex.
*/
-static void update_cpu_domains(struct cpuset *cur)
+static void update_cpu_domains(void)
{
- struct cpuset *c, *par = cur->parent;
- cpumask_t pspan, cspan;
+ cpumask_t non_partitioned;
- if (par == NULL || cpus_empty(cur->cpus_allowed))
- return;
-
- /*
- * Get all cpus from parent's cpus_allowed not part of exclusive
- * children
- */
- pspan = par->cpus_allowed;
- list_for_each_entry(c, &par->children, sibling) {
- if (is_cpu_exclusive(c))
- cpus_andnot(pspan, pspan, c->cpus_allowed);
- }
- if (!is_cpu_exclusive(cur)) {
- cpus_or(pspan, pspan, cur->cpus_allowed);
- if (cpus_equal(pspan, cur->cpus_allowed))
- return;
- cspan = CPU_MASK_NONE;
- } else {
- if (cpus_empty(pspan))
- return;
- cspan = cur->cpus_allowed;
- /*
- * Get all cpus from current cpuset's cpus_allowed not part
- * of exclusive children
- */
- list_for_each_entry(c, &cur->children, sibling) {
- if (is_cpu_exclusive(c))
- cpus_andnot(cspan, cspan, c->cpus_allowed);
- }
- }
+ BUG_ON(!mutex_is_locked(&manage_mutex));
lock_cpu_hotplug();
- partition_sched_domains(&pspan, &cspan);
+ non_partitioned = top_cpuset.cpus_allowed;
+ update_cpu_domains_children(&top_cpuset, &non_partitioned);
+ partition_sched_domains(&non_partitioned);
unlock_cpu_hotplug();
}
/*
+ * Same as above except called with lock_cpu_hotplug and without manage_mutex.
+ */
+
+int cpuset_hotplug_update_sched_domains(void)
+{
+ cpumask_t non_partitioned;
+
+ non_partitioned = top_cpuset.cpus_allowed;
+ update_cpu_domains_children(&top_cpuset, &non_partitioned);
+ return partition_sched_domains(&non_partitioned);
+}
+
+/*
* Call with manage_mutex held. May take callback_mutex during call.
*/
@@ -833,8 +836,8 @@ static int update_cpumask(struct cpuset
mutex_lock(&callback_mutex);
cs->cpus_allowed = trialcs.cpus_allowed;
mutex_unlock(&callback_mutex);
- if (is_cpu_exclusive(cs) && !cpus_unchanged)
- update_cpu_domains(cs);
+ if (!cpus_unchanged)
+ update_cpu_domains();
return 0;
}
@@ -1067,7 +1070,7 @@ static int update_flag(cpuset_flagbits_t
mutex_unlock(&callback_mutex);
if (cpu_exclusive_changed)
- update_cpu_domains(cs);
+ update_cpu_domains();
return 0;
}
@@ -1931,19 +1934,9 @@ static int cpuset_mkdir(struct inode *di
return cpuset_create(c_parent, dentry->d_name.name, mode | S_IFDIR);
}
-/*
- * Locking note on the strange update_flag() call below:
- *
- * If the cpuset being removed is marked cpu_exclusive, then simulate
- * turning cpu_exclusive off, which will call update_cpu_domains().
- * The lock_cpu_hotplug() call in update_cpu_domains() must not be
- * made while holding callback_mutex. Elsewhere the kernel nests
- * callback_mutex inside lock_cpu_hotplug() calls. So the reverse
- * nesting would risk an ABBA deadlock.
- */
-
static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
+ int is_exclusive;
struct cpuset *cs = dentry->d_fsdata;
struct dentry *d;
struct cpuset *parent;
@@ -1961,13 +1954,8 @@ static int cpuset_rmdir(struct inode *un
mutex_unlock(&manage_mutex);
return -EBUSY;
}
- if (is_cpu_exclusive(cs)) {
- int retval = update_flag(CS_CPU_EXCLUSIVE, cs, "0");
- if (retval < 0) {
- mutex_unlock(&manage_mutex);
- return retval;
- }
- }
+ is_exclusive = is_cpu_exclusive(cs);
+
parent = cs->parent;
mutex_lock(&callback_mutex);
set_bit(CS_REMOVED, &cs->flags);
@@ -1982,8 +1970,13 @@ static int cpuset_rmdir(struct inode *un
mutex_unlock(&callback_mutex);
if (list_empty(&parent->children))
check_for_release(parent, &pathbuf);
+
+ if (is_exclusive)
+ update_cpu_domains();
+
mutex_unlock(&manage_mutex);
cpuset_release_agent(pathbuf);
+
return 0;
}
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c 2006-10-19 19:24:48.000000000 +1000
+++ linux-2.6/kernel/sched.c 2006-10-19 20:21:50.000000000 +1000
@@ -6586,6 +6586,9 @@ error:
*/
static int arch_init_sched_domains(const cpumask_t *cpu_map)
{
+#ifdef CONFIG_CPUSETS
+ return cpuset_hotplug_update_sched_domains();
+#else
cpumask_t cpu_default_map;
int err;
@@ -6599,6 +6602,7 @@ static int arch_init_sched_domains(const
err = build_sched_domains(&cpu_default_map);
return err;
+#endif
}
static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
@@ -6622,29 +6626,26 @@ static void detach_destroy_domains(const
/*
* Partition sched domains as specified by the cpumasks below.
- * This attaches all cpus from the cpumasks to the NULL domain,
+ * This attaches all cpus from the partition to the NULL domain,
* waits for a RCU quiescent period, recalculates sched
- * domain information and then attaches them back to the
- * correct sched domains
- * Call with hotplug lock held
+ * domain information and then attaches them back to their own
+ * isolated partition.
+ *
+ * Called with hotplug lock held
+ *
+ * Returns 0 on success.
*/
-int partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
+int partition_sched_domains(cpumask_t *partition)
{
+ cpumask_t non_isolated_cpus;
cpumask_t change_map;
- int err = 0;
- cpus_and(*partition1, *partition1, cpu_online_map);
- cpus_and(*partition2, *partition2, cpu_online_map);
- cpus_or(change_map, *partition1, *partition2);
+ cpus_andnot(non_isolated_cpus, cpu_online_map, cpu_isolated_map);
+ cpus_and(change_map, *partition, non_isolated_cpus);
/* Detach sched domains from all of the affected cpus */
detach_destroy_domains(&change_map);
- if (!cpus_empty(*partition1))
- err = build_sched_domains(partition1);
- if (!err && !cpus_empty(*partition2))
- err = build_sched_domains(partition2);
-
- return err;
+ return build_sched_domains(&change_map);
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h 2006-10-19 20:02:24.000000000 +1000
+++ linux-2.6/include/linux/sched.h 2006-10-19 20:02:30.000000000 +1000
@@ -707,8 +707,7 @@ struct sched_domain {
#endif
};
-extern int partition_sched_domains(cpumask_t *partition1,
- cpumask_t *partition2);
+extern int partition_sched_domains(cpumask_t *partition);
/*
* Maximum cache size the migration-costs auto-tuning code will
Index: linux-2.6/include/linux/cpuset.h
===================================================================
--- linux-2.6.orig/include/linux/cpuset.h 2006-10-19 20:07:24.000000000 +1000
+++ linux-2.6/include/linux/cpuset.h 2006-10-19 20:21:08.000000000 +1000
@@ -14,6 +14,8 @@
#ifdef CONFIG_CPUSETS
+extern int cpuset_hotplug_update_sched_domains(void);
+
extern int number_of_cpusets; /* How many cpusets are defined in system? */
extern int cpuset_init_early(void);
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