linux-kernel - [PATCH v2 1/7] cpusets, hotplug: Implement cpuset tree traversal in a helper function

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120504191731.4603.56791.stgit@srivatsabhat>
Date:	Sat, 05 May 2012 00:47:48 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	a.p.zijlstra@...llo.nl, mingo@...nel.org, pjt@...gle.com,
	paul@...lmenage.org, akpm@...ux-foundation.org
Cc:	rjw@...k.pl, nacc@...ibm.com, paulmck@...ux.vnet.ibm.com,
	tglx@...utronix.de, seto.hidetoshi@...fujitsu.com, rob@...dley.net,
	tj@...nel.org, mschmidt@...hat.com, berrange@...hat.com,
	nikunj@...ux.vnet.ibm.com, vatsa@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-pm@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com
Subject: [PATCH v2 1/7] cpusets,
 hotplug: Implement cpuset tree traversal in a helper function

At present, the functions that deal with cpusets during CPU/Mem hotplug
are quite messy, since a lot of the functionality is mixed up without clear
separation. And this takes a toll on optimization as well. For example,
the function cpuset_update_active_cpus() is called on both CPU offline and CPU
online events; and it invokes scan_for_empty_cpusets(), which makes sense
only for CPU offline events. And hence, the current code ends up unnecessarily
traversing the cpuset tree during CPU online also.

As a first step towards cleaning up those functions, encapsulate the cpuset
tree traversal in a helper function, so as to facilitate upcoming changes.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: stable@...r.kernel.org
---

 kernel/cpuset.c |   26 ++++++++++++++++++--------
 1 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 14f7070..23e5da6 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2000,6 +2000,23 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
 	move_member_tasks_to_cpuset(cs, parent);
 }
 
+static struct cpuset *traverse_cpusets(struct list_head *queue)
+{
+	struct cpuset *cp;
+	struct cpuset *child;	/* scans child cpusets of cp */
+	struct cgroup *cont;
+
+	cp = list_first_entry(queue, struct cpuset, stack_list);
+	list_del(queue->next);
+	list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
+		child = cgroup_cs(cont);
+		list_add_tail(&child->stack_list, queue);
+	}
+
+	return cp;
+}
+
+
 /*
  * Walk the specified cpuset subtree and look for empty cpusets.
  * The tasks of such cpuset must be moved to a parent cpuset.
@@ -2019,19 +2036,12 @@ static void scan_for_empty_cpusets(struct cpuset *root)
 {
 	LIST_HEAD(queue);
 	struct cpuset *cp;	/* scans cpusets being updated */
-	struct cpuset *child;	/* scans child cpusets of cp */
-	struct cgroup *cont;
 	static nodemask_t oldmems;	/* protected by cgroup_mutex */
 
 	list_add_tail((struct list_head *)&root->stack_list, &queue);
 
 	while (!list_empty(&queue)) {
-		cp = list_first_entry(&queue, struct cpuset, stack_list);
-		list_del(queue.next);
-		list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
-			child = cgroup_cs(cont);
-			list_add_tail(&child->stack_list, &queue);
-		}
+		cp = traverse_cpusets(&queue);
 
 		/* Continue past cpusets with all cpus, mems online */
 		if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&

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