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 <hejia...@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.

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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