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Date: Mon, 4 Apr 2016 13:11:47 -0400
From: Waiman Long <waiman.long@....com>
To: Nikolay Borisov <kernel@...p.com>
CC: Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
<linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
Scott J Norton <scott.norton@....com>,
Douglas Hatch <doug.hatch@....com>,
Toshimitsu Kani <toshi.kani@....com>
Subject: Re: [PATCH 2/3] percpu_stats: Simple per-cpu statistics count helper
functions
On 04/04/2016 03:36 AM, Nikolay Borisov wrote:
>
> On 04/02/2016 06:09 AM, Waiman Long wrote:
>> This patch introduces a set of simple per-cpu statictics count helper
>> functions that can be used by other kernel subsystems for keeping
>> track of the number of events that happens. It is per-cpu based to
>> reduce overhead and improve accuracy of the counter. Using per-cpu
>> counter is usually overkill for such purpose.
>>
>> The following APIs are provided:
>>
>> - int percpu_stats_init(struct percpu_stats *pcs, int num)
>> Initialize the per-cpu statictics counts structure which should have
>> the given number of statistics counts. Return -ENOMEM on error.
>>
>> - void percpu_stats_destroy(struct percpu_stats *pcs)
>> Free the percpu memory allocated.
>>
>> - void percpu_stats_inc(struct percpu_stats *pcs, int stat)
>> void percpu_stats_dec(struct percpu_stats *pcs, int stat)
>> Increment and decrement the given per-cpu statistics count.
>>
>> - unsigned long percpu_stats_sum(struct percpu_stats *pcs, int stat)
>> Return the current aggregated sum of the given statistics count.
>>
>> - void percpu_stats_reset(struct percpu_stats *pcs)
>> Clear all the statistics counts defined in the given percpu_stats
>> structure.
>>
>> Signed-off-by: Waiman Long<Waiman.Long@....com>
>> ---
>> include/linux/percpu_stats.h | 103 ++++++++++++++++++++++++++++++++++++++++++
>> 1 files changed, 103 insertions(+), 0 deletions(-)
>> create mode 100644 include/linux/percpu_stats.h
> Just one minor nit below.
> [..]
>> +static inline void
>> +__percpu_stats_add(struct percpu_stats *pcs, int stat, int cnt)
>> +{
>> + unsigned long *pstat;
>> +
>> + if ((unsigned int)stat>= pcs->nstats)
>> + return;
>> + preempt_disable();
>> + pstat = this_cpu_ptr(&pcs->stats[stat]);
>> + *pstat += cnt;
>> + preempt_enable();
>> +}
> pstat = get_cpu_ptr(&pcs->stats[stat]);
> *pstat += cnt;
> put_cpu_ptr(&pcs->stats[stat]);
>
> It will generate identical code but this one uses APIs, making the
> intention clearer. But as I said this is just a minor nit.
>
> you can add my Reviewed-by: Nikolay Borisov<kernel@...p.com> for this
> particular patch.
Yes, that will certainly make it look nicer. I will update the patch
once I get feedback from my other ext4 patches.
Cheers,
Longman
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