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Date: Mon, 4 Apr 2016 10:36:09 +0300 From: Nikolay Borisov <kernel@...p.com> To: Waiman Long <Waiman.Long@....com>, Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com> Cc: 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 04/02/2016 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.
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