Re: [RFC PATCH v3 3/7] proc: Reduce cache miss in snmp6_seq_show

[hejianet]

On 9/13/16 3:05 AM, Marcelo wrote:
> On Fri, Sep 09, 2016 at 02:33:58PM +0800, Jia He wrote:
> > This is to use the generic interface snmp_get_cpu_field{,64}_batch to
> > aggregate the data by going through all the items of each cpu sequentially.
> >
> > Signed-off-by: Jia He <hejianet@xxxxxxxxx>
> > ---
> >   net/ipv6/proc.c | 32 +++++++++++++++++++++++---------
> >   1 file changed, 23 insertions(+), 9 deletions(-)
> >
> > diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
> > index 679253d0..50ba2c3 100644
> > --- a/net/ipv6/proc.c
> > +++ b/net/ipv6/proc.c
> > @@ -30,6 +30,11 @@
> >   #include <net/transp_v6.h>
> >   #include <net/ipv6.h>
> >   
> > +#define MAX4(a, b, c, d) \
> > +	max_t(u32, max_t(u32, a, b), max_t(u32, c, d))
> > +#define SNMP_MIB_MAX MAX4(UDP_MIB_MAX, TCP_MIB_MAX, \
> > +			IPSTATS_MIB_MAX, ICMP_MIB_MAX)
> > +
> >   static int sockstat6_seq_show(struct seq_file *seq, void *v)
> >   {
> >   	struct net *net = seq->private;
> > @@ -192,13 +197,19 @@ static void snmp6_seq_show_item(struct seq_file *seq, void __percpu *pcpumib,
> >   				const struct snmp_mib *itemlist)
> >   {
> >   	int i;
> > -	unsigned long val;
> > -
> > -	for (i = 0; itemlist[i].name; i++) {
> > -		val = pcpumib ?
> > -			snmp_fold_field(pcpumib, itemlist[i].entry) :
> > -			atomic_long_read(smib + itemlist[i].entry);
> > -		seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name, val);
> > +	unsigned long buff[SNMP_MIB_MAX];
> > +
> > +	memset(buff, 0, sizeof(unsigned long) * SNMP_MIB_MAX);
> This memset() could be moved...
>
> > +
> > +	if (pcpumib) {
> ... here, so it's not executed if it hits the else block.
Thanks for the suggestion
B.R.
Jia
> > +		snmp_get_cpu_field_batch(buff, itemlist, pcpumib);
> > +		for (i = 0; itemlist[i].name; i++)
> > +			seq_printf(seq, "%-32s\t%lu\n",
> > +				   itemlist[i].name, buff[i]);
> > +	} else {
> > +		for (i = 0; itemlist[i].name; i++)
> > +			seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name,
> > +				   atomic_long_read(smib + itemlist[i].entry));
> >   	}
> >   }
> >   
> > @@ -206,10 +217,13 @@ static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu *mib,
> >   				  const struct snmp_mib *itemlist, size_t syncpoff)
> >   {
> >   	int i;
> > +	u64 buff64[SNMP_MIB_MAX];
> > +
> > +	memset(buff64, 0, sizeof(unsigned long) * SNMP_MIB_MAX);
> >   
> > +	snmp_get_cpu_field64_batch(buff64, itemlist, mib, syncpoff);
> >   	for (i = 0; itemlist[i].name; i++)
> > -		seq_printf(seq, "%-32s\t%llu\n", itemlist[i].name,
> > -			   snmp_fold_field64(mib, itemlist[i].entry, syncpoff));
> > +		seq_printf(seq, "%-32s\t%llu\n", itemlist[i].name, buff64[i]);
> >   }
> >   
> >   static int snmp6_seq_show(struct seq_file *seq, void *v)
> > --
> > 1.8.3.1
> >
> > --
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