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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] sched: cpuacct: Use bigger percpu counter batch values for stats counters
Cc: kosaki.motohiro@jp.fujitsu.com, Anton Blanchard <anton@samba.org>,
       Bharata B Rao <bharata@linux.vnet.ibm.com>, Ingo Molnar <mingo@elte.hu>,
       Balbir Singh <balbir@linux.vnet.ibm.com>, mingo@redhat.com,
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       tglx@linutronix.de, kamezawa.hiroyu@jp.fujitsu.com,
       Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>,
       Heiko Carstens <heiko.carstens@de.ibm.com>, linux390@de.ibm.com
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Date: Tue, 26 Jan 2010 08:44:15 +0900 (JST)
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> On Mon, 18 Jan 2010 15:41:42 +1100
> Anton Blanchard <anton@samba.org> wrote:
> 
> > When CONFIG_VIRT_CPU_ACCOUNTING and CONFIG_CGROUP_CPUACCT are enabled we can
> > call cpuacct_update_stats with values much larger than percpu_counter_batch.
> > This means the call to percpu_counter_add will always add to the global count
> > which is protected by a spinlock and we end up with a global spinlock in
> > the scheduler.
> 
> When one looks at the end result:

We have about 32 jiffies batch both with or without CONFIG_VIRT_CPU_ACCOUNTING.
Then, The enduser can looks some jiffies after.