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Message-Id: <20090428153611.EBC6.A69D9226@jp.fujitsu.com>
Date: Tue, 28 Apr 2009 15:53:32 +0900 (JST)
From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To: LKML <linux-kernel@...r.kernel.org>,
Bharata B Rao <bharata@...ux.vnet.ibm.com>,
Balaji Rao <balajirrao@...il.com>,
Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
seto.hidetoshi@...fujitsu.com
Cc: kosaki.motohiro@...fujitsu.com
Subject: [PATCH] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count
I'm not cpuacct expert. please give me comment.
====================
Subject: [PATCH] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime caching
impact: little performance improvement
cpuacct_update_stats() is called at every tick updating. and it use percpu_counter
for avoiding performance degression.
Unfortunately, it doesn't works on VIRT_CPU_ACCOUNTING=y environment properly.
if VIRT_CPU_ACCOUNTING=y, every tick update much than 1000 cputime.
Thus every percpu_counter_add() makes spinlock grabbing and update non-percpu-variable.
This patch change the batch rule. now, every cpu can store "percpu_counter_bach x jiffies"
cputime in percpu cache.
it mean this patch don't have behavior change if VIRT_CPU_ACCOUNTING=n, but
works well on VIRT_CPU_ACCOUNTING=y too.
Cc: Bharata B Rao <bharata@...ux.vnet.ibm.com>
Cc: Balaji Rao <balajirrao@...il.com>
Cc: Dhaval Giani <dhaval@...ux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
kernel/sched.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
Index: b/kernel/sched.c
===================================================================
--- a/kernel/sched.c 2009-04-28 14:18:36.000000000 +0900
+++ b/kernel/sched.c 2009-04-28 15:18:07.000000000 +0900
@@ -10117,6 +10117,7 @@ struct cpuacct {
};
struct cgroup_subsys cpuacct_subsys;
+static s32 cpuacct_batch;
/* return cpu accounting group corresponding to this container */
static inline struct cpuacct *cgroup_ca(struct cgroup *cgrp)
@@ -10146,6 +10147,9 @@ static struct cgroup_subsys_state *cpuac
if (!ca->cpuusage)
goto out_free_ca;
+ if (!cpuacct_batch)
+ cpuacct_batch = jiffies_to_cputime(percpu_counter_batch);
+
for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
if (percpu_counter_init(&ca->cpustat[i], 0))
goto out_free_counters;
@@ -10342,7 +10346,7 @@ static void cpuacct_update_stats(struct
ca = task_ca(tsk);
do {
- percpu_counter_add(&ca->cpustat[idx], val);
+ __percpu_counter_add(&ca->cpustat[idx], val, cpuacct_batch);
ca = ca->parent;
} while (ca);
rcu_read_unlock();
--
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