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

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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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