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SubjectRe: [RFC PATCH v3 3/7] proc: Reduce cache miss in snmp6_seq_show
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@gmail.com>
> ---
> 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.

> + 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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