[PATCH v5 3/5] cpusets, hotplug: Restructure functions that are invoked during hotplug

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


Separate out the cpuset related handling for CPU/Memory online/offline.
This also helps us exploit the most obvious and basic level of optimization
that any notification mechanism (CPU/Mem online/offline) has to offer us:
"We *know* why we have been invoked. So stop pretending that we are lost,
and do only the necessary amount of processing!".

And while at it, rename scan_for_empty_cpusets() to
scan_cpusets_upon_hotplug(), which is more appropriate considering how
it is restructured.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---

 include/linux/cpuset.h |    4 +-
 kernel/cpuset.c        |   88 +++++++++++++++++++++++++++++++++---------------
 kernel/sched/core.c    |    4 +-
 3 files changed, 65 insertions(+), 31 deletions(-)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 668f66b..838320f 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -20,7 +20,7 @@ extern int number_of_cpusets;	/* How many cpusets are defined in system? */
 
 extern int cpuset_init(void);
 extern void cpuset_init_smp(void);
-extern void cpuset_update_active_cpus(void);
+extern void cpuset_update_active_cpus(bool cpu_online);
 extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
 extern void cpuset_cpus_allowed_fallback(struct task_struct *p);
 extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@@ -124,7 +124,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
 static inline int cpuset_init(void) { return 0; }
 static inline void cpuset_init_smp(void) {}
 
-static inline void cpuset_update_active_cpus(void)
+static inline void cpuset_update_active_cpus(bool cpu_online)
 {
 	partition_sched_domains(1, NULL, NULL);
 }
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 15926f8..276a35a 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -147,6 +147,12 @@ typedef enum {
 	CS_SPREAD_SLAB,
 } cpuset_flagbits_t;
 
+/* the type of hotplug event */
+enum hotplug_event {
+	CPUSET_CPU_OFFLINE,
+	CPUSET_MEM_OFFLINE,
+};
+
 /* convenient tests for these bits */
 static inline int is_cpu_exclusive(const struct cpuset *cs)
 {
@@ -2027,8 +2033,10 @@ static struct cpuset *cpuset_next(struct list_head *queue)
 
 
 /*
- * Walk the specified cpuset subtree and look for empty cpusets.
- * The tasks of such cpuset must be moved to a parent cpuset.
+ * Walk the specified cpuset subtree upon a hotplug operation (CPU/Memory
+ * online/offline) and update the cpusets accordingly.
+ * For regular CPU/Mem hotplug, look for empty cpusets; the tasks of such
+ * cpuset must be moved to a parent cpuset.
  *
  * Called with cgroup_mutex held.  We take callback_mutex to modify
  * cpus_allowed and mems_allowed.
@@ -2041,38 +2049,58 @@ static struct cpuset *cpuset_next(struct list_head *queue)
  * that has tasks along with an empty 'mems'.  But if we did see such
  * a cpuset, we'd handle it just like we do if its 'cpus' was empty.
  */
-static void scan_for_empty_cpusets(struct cpuset *root)
+static void
+scan_cpusets_upon_hotplug(struct cpuset *root, enum hotplug_event event)
 {
 	LIST_HEAD(queue);
-	struct cpuset *cp;	/* scans cpusets being updated */
+	struct cpuset *cp;		/* scans cpusets being updated */
 	static nodemask_t oldmems;	/* protected by cgroup_mutex */
 
 	list_add_tail((struct list_head *)&root->stack_list, &queue);
 
-	while ((cp = cpuset_next(&queue)) != NULL) {
+	switch (event) {
+	case CPUSET_CPU_OFFLINE:
+		while ((cp = cpuset_next(&queue)) != NULL) {
 
-		/* Continue past cpusets with all cpus, mems online */
-		if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&
-		    nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY]))
-			continue;
+			/* Continue past cpusets with all cpus online */
+			if (cpumask_subset(cp->cpus_allowed, cpu_active_mask))
+				continue;
 
-		oldmems = cp->mems_allowed;
+			/* Remove offline cpus from this cpuset. */
+			mutex_lock(&callback_mutex);
+			cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
+							cpu_active_mask);
+			mutex_unlock(&callback_mutex);
 
-		/* Remove offline cpus and mems from this cpuset. */
-		mutex_lock(&callback_mutex);
-		cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
-			    cpu_active_mask);
-		nodes_and(cp->mems_allowed, cp->mems_allowed,
+			/* Move tasks from the empty cpuset to a parent */
+			if (cpumask_empty(cp->cpus_allowed))
+				remove_tasks_in_empty_cpuset(cp);
+			else
+				update_tasks_cpumask(cp, NULL);
+		}
+		break;
+
+	case CPUSET_MEM_OFFLINE:
+		while ((cp = cpuset_next(&queue)) != NULL) {
+
+			/* Continue past cpusets with all mems online */
+			if (nodes_subset(cp->mems_allowed,
+					node_states[N_HIGH_MEMORY]))
+				continue;
+
+			oldmems = cp->mems_allowed;
+
+			/* Remove offline mems from this cpuset. */
+			mutex_lock(&callback_mutex);
+			nodes_and(cp->mems_allowed, cp->mems_allowed,
 						node_states[N_HIGH_MEMORY]);
-		mutex_unlock(&callback_mutex);
+			mutex_unlock(&callback_mutex);
 
-		/* Move tasks from the empty cpuset to a parent */
-		if (cpumask_empty(cp->cpus_allowed) ||
-		     nodes_empty(cp->mems_allowed))
-			remove_tasks_in_empty_cpuset(cp);
-		else {
-			update_tasks_cpumask(cp, NULL);
-			update_tasks_nodemask(cp, &oldmems, NULL);
+			/* Move tasks from the empty cpuset to a parent */
+			if (nodes_empty(cp->mems_allowed))
+				remove_tasks_in_empty_cpuset(cp);
+			else
+				update_tasks_nodemask(cp, &oldmems, NULL);
 		}
 	}
 }
@@ -2091,8 +2119,11 @@ static void scan_for_empty_cpusets(struct cpuset *root)
  *
  * Called within get_online_cpus().  Needs to call cgroup_lock()
  * before calling generate_sched_domains().
+ *
+ * @cpu_online: Indicates whether this is a CPU online event (true) or
+ * a CPU offline event (false).
  */
-void cpuset_update_active_cpus(void)
+void cpuset_update_active_cpus(bool cpu_online)
 {
 	struct sched_domain_attr *attr;
 	cpumask_var_t *doms;
@@ -2102,7 +2133,10 @@ void cpuset_update_active_cpus(void)
 	mutex_lock(&callback_mutex);
 	cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
 	mutex_unlock(&callback_mutex);
-	scan_for_empty_cpusets(&top_cpuset);
+
+	if (!cpu_online)
+		scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_CPU_OFFLINE);
+
 	ndoms = generate_sched_domains(&doms, &attr);
 	cgroup_unlock();
 
@@ -2133,9 +2167,9 @@ static int cpuset_track_online_nodes(struct notifier_block *self,
 	case MEM_OFFLINE:
 		/*
 		 * needn't update top_cpuset.mems_allowed explicitly because
-		 * scan_for_empty_cpusets() will update it.
+		 * scan_cpusets_upon_hotplug() will update it.
 		 */
-		scan_for_empty_cpusets(&top_cpuset);
+		scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_MEM_OFFLINE);
 		break;
 	default:
 		break;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9c6ce0c..b5a0a0c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6838,7 +6838,7 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
 
 	case CPU_ONLINE:
 	case CPU_DOWN_FAILED:
-		cpuset_update_active_cpus();
+		cpuset_update_active_cpus(true);
 		break;
 	default:
 		return NOTIFY_DONE;
@@ -6851,7 +6851,7 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
 {
 	switch (action) {
 	case CPU_DOWN_PREPARE:
-		cpuset_update_active_cpus();
+		cpuset_update_active_cpus(false);
 		break;
 	case CPU_DOWN_PREPARE_FROZEN:
 		num_cpus_frozen++;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/


[Other Archives]     [Linux Kernel Newbies]     [Linux Driver Development]     [Fedora Kernel]     [Linux Kernel Testers]     [Linux SH]     [Linux Omap]     [Linux Kbuild]     [Linux Tape]     [Linux Input]     [Linux Kernel Janitors]     [Linux Kernel Packagers]     [Linux Doc]     [Linux Man Pages]     [Linux API]     [Linux Memory Management]     [Linux Modules]     [Linux Standards]     [Kernel Announce]     [Netdev]     [Git]     [Linux PCI]     Linux CAN Development     [Linux I2C]     [Linux RDMA]     [Linux NUMA]     [Netfilter]     [Netfilter Devel]     [SELinux]     [Bugtraq]     [FIO]     [Linux Perf Users]     [Linux Serial]     [Linux PPP]     [Linux ISDN]     [Linux Next]     [Kernel Stable Commits]     [Linux Tip Commits]     [Kernel MM Commits]     [Linux Security Module]     [AutoFS]     [Filesystem Development]     [Ext3 Filesystem]     [Linux bcache]     [Ext4 Filesystem]     [Linux BTRFS]     [Linux CEPH Filesystem]     [Linux XFS]     [XFS]     [Linux NFS]     [Linux CIFS]     [Ecryptfs]     [Linux NILFS]     [Linux Cachefs]     [Reiser FS]     [Initramfs]     [Linux FB Devel]     [Linux OpenGL]     [DRI Devel]     [Fastboot]     [Linux RT Users]     [Linux RT Stable]     [eCos]     [Corosync]     [Linux Clusters]     [LVS Devel]     [Hot Plug]     [Linux Virtualization]     [KVM]     [KVM PPC]     [KVM ia64]     [Linux Containers]     [Linux Hexagon]     [Linux Cgroups]     [Util Linux]     [Wireless]     [Linux Bluetooth]     [Bluez Devel]     [Ethernet Bridging]     [Embedded Linux]     [Barebox]     [Linux MMC]     [Linux IIO]     [Sparse]     [Smatch]     [Linux Arch]     [x86 Platform Driver]     [Linux ACPI]     [Linux IBM ACPI]     [LM Sensors]     [CPU Freq]     [Linux Power Management]     [Linmodems]     [Linux DCCP]     [Linux SCTP]     [ALSA Devel]     [Linux USB]     [Linux PA RISC]     [Linux Samsung SOC]     [MIPS Linux]     [IBM S/390 Linux]     [ARM Linux]     [ARM Kernel]     [ARM MSM]     [Tegra Devel]     [Sparc Linux]     [Linux Security]     [Linux Sound]     [Linux Media]     [Video 4 Linux]     [Linux IRDA Users]     [Linux for the blind]     [Linux RAID]     [Linux ATA RAID]     [Device Mapper]     [Linux SCSI]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Linux IDE]     [Linux SMP]     [Linux AXP]     [Linux Alpha]     [Linux M68K]     [Linux ia64]     [Linux 8086]     [Linux x86_64]     [Linux Config]     [Linux Apps]     [Linux MSDOS]     [Linux X.25]     [Linux Crypto]     [DM Crypt]     [Linux Trace Users]     [Linux Btrace]     [Linux Watchdog]     [Utrace Devel]     [Linux C Programming]     [Linux Assembly]     [Dash]     [DWARVES]     [Hail Devel]     [Linux Kernel Debugger]     [Linux gcc]     [Gcc Help]     [X.Org]     [Wine]

Add to Google Powered by Linux

[Older Kernel Discussion]     [Yosemite National Park Forum]     [Large Format Photos]     [Gimp]     [Yosemite Photos]     [Stuff]