linux-kernel - Re: [PATCH 3/9] mm/vmstat: Convert NUMA statistics to basic NUMA counters

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Message-ID: <20210423083208.GB4239@techsingularity.net>
Date:   Fri, 23 Apr 2021 09:32:08 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux-RT-Users <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/9] mm/vmstat: Convert NUMA statistics to basic NUMA
 counters

On Thu, Apr 22, 2021 at 05:18:38PM +0200, Vlastimil Babka wrote:
> > +
> > +#ifdef CONFIG_NUMA
> > +static void fold_vm_zone_numa_events(struct zone *zone)
> >  {
> > -	int i;
> > -	int changes = 0;
> > +	int zone_numa_events[NR_VM_NUMA_EVENT_ITEMS] = { 0, };
> 
> Should this be long? pzstats are, the global counters too, so seems weird to use
> int as intermediate sum counter.
> 

While overflow can happen eventually, unsigned long defers the problem
so yes, I'll make it unsigned long.

> >  #ifdef CONFIG_NUMA
> > -		for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
> > -			if (pzstats->vm_numa_stat_diff[i]) {
> > +		for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++) {
> > +			if (pzstats->vm_numa_event[i]) {
> >  				int v;
> 
> Also long?
> 

Same.

> >  /*
> > @@ -939,43 +914,36 @@ void cpu_vm_stats_fold(int cpu)
> >   */
> >  void drain_zonestat(struct zone *zone, struct per_cpu_zonestat *pzstats)
> >  {
> > -	int i;
> > +	int i, v;
> 
> And the 'v' here. Maybe keep using local to each loop below and make it long for
> the NUMA one?
> 

I just made it unsigned long. There is no storage advantage to changing
type in a local scoped variable.

Thanks

-- 
Mel Gorman
SUSE Labs