linux-kernel - [PATCH v2 2/3] Reuse cgroup's parent pointer

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 for Android: free password hash cracker in your pocket

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

Date:	Mon, 28 Nov 2011 14:45:18 -0200
From:	Glauber Costa <glommer@...allels.com>
To:	linux-kernel@...r.kernel.org
Cc:	paul@...lmenage.org, lizf@...fujitsu.com, daniel.lezcano@...e.fr,
	a.p.zijlstra@...llo.nl, jbottomley@...allels.com, pjt@...gle.com,
	cgroups@...r.kernel.org, bsingharora@...il.com, devel@...nvz.org,
	kamezawa.hiroyu@...fujitsu.com,
	Glauber Costa <glommer@...allels.com>
Subject: [PATCH v2 2/3] Reuse cgroup's parent pointer

We already have a pointer to the cgroup parent (whose data is more likely
to be in the cache than this, anyway), so there is no need to have this one
in cpuacct.

This patch makes the underlying cgroup be used instead.

Signed-off-by: Glauber Costa <glommer@...allels.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC: Paul Tuner <pjt@...gle.com>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 kernel/sched/core.c |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e9e0c19..c36f926 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7840,7 +7840,6 @@ struct cpuacct {
 	/* cpuusage holds pointer to a u64-type object on every cpu */
 	u64 __percpu *cpuusage;
 	struct percpu_counter cpustat[CPUACCT_STAT_NSTATS];
-	struct cpuacct *parent;
 };
 
 struct cgroup_subsys cpuacct_subsys;
@@ -7859,6 +7858,13 @@ static inline struct cpuacct *task_ca(struct task_struct *tsk)
 			    struct cpuacct, css);
 }
 
+static inline struct cpuacct *parent_ca(struct cpuacct *ca)
+{
+	if (!ca || !ca->css.cgroup->parent)
+		return NULL;
+	return cgroup_ca(ca->css.cgroup->parent);
+}
+
 /* create a new cpu accounting group */
 static struct cgroup_subsys_state *cpuacct_create(
 	struct cgroup_subsys *ss, struct cgroup *cgrp)
@@ -7877,9 +7883,6 @@ static struct cgroup_subsys_state *cpuacct_create(
 		if (percpu_counter_init(&ca->cpustat[i], 0))
 			goto out_free_counters;
 
-	if (cgrp->parent)
-		ca->parent = cgroup_ca(cgrp->parent);
-
 	return &ca->css;
 
 out_free_counters:
@@ -8046,7 +8049,7 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 
 	ca = task_ca(tsk);
 
-	for (; ca; ca = ca->parent) {
+	for (; ca; ca = parent_ca(ca)) {
 		u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
 		*cpuusage += cputime;
 	}
@@ -8088,7 +8091,7 @@ void cpuacct_update_stats(struct task_struct *tsk,
 
 	do {
 		__percpu_counter_add(&ca->cpustat[idx], val, batch);
-		ca = ca->parent;
+		ca = parent_ca(ca);
 	} while (ca);
 	rcu_read_unlock();
 }
-- 
1.7.6.4

--
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/