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Date: Mon, 14 Mar 2016 02:08:06 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Cc: linux-mm@kvack.org, hughd@google.com, riel@redhat.com,
        akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
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Subject: Re: [PATCH v2 1/2] mm, vmstat: calculate particular vm event
Message-ID: <20160313230806.GA10438@node.shutemov.name>
References: <1457861335-23297-1-git-send-email-ebru.akagunduz@gmail.com>
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On Sun, Mar 13, 2016 at 11:28:54AM +0200, Ebru Akagunduz wrote:
> Currently, vmstat can calculate specific vm event with all_vm_events()
> however it allocates all vm events to stack. This patch introduces
> a helper to sum value of a specific vm event over all cpu, without
> loading all the events.
> 
> Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
> ---
> Changes in v2:
>  - this patch newly created in this version
>  - create sum event function to
>    calculate particular vm event (Kirill A. Shutemov)
> 
>  include/linux/vmstat.h |  2 ++
>  mm/vmstat.c            | 12 ++++++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index 73fae8c..add0cc1 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -53,6 +53,8 @@ static inline void count_vm_events(enum vm_event_item item, long delta)
>  
>  extern void all_vm_events(unsigned long *);
>  
> +extern unsigned long sum_vm_event(enum vm_event_item item);
> +
>  extern void vm_events_fold_cpu(int cpu);
>  
>  #else

You need dumy definition of the function for !CONFIG_VM_EVENT_COUNTERS
case here. Otherwise build will fail. See 0-day report.

Otherwise looks good to me:

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 5e43004..b76d664 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -34,6 +34,18 @@
>  DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
>  EXPORT_PER_CPU_SYMBOL(vm_event_states);
>  
> +unsigned long sum_vm_event(enum vm_event_item item)
> +{
> +	int cpu;
> +	unsigned long ret = 0;
> +
> +	get_online_cpus();
> +	for_each_online_cpu(cpu)
> +		ret += per_cpu(vm_event_states, cpu).event[item];
> +	put_online_cpus();
> +	return ret;
> +}
> +
>  static void sum_vm_events(unsigned long *ret)
>  {
>  	int cpu;
> -- 
> 1.9.1
> 
> --
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-- 
 Kirill A. Shutemov