net: proc: speedup /proc/net/netstat

Use cache friendly helpers to better use cpu caches
while reading /proc/net/netstat

Tested on a platform with 256 threads (AMD Rome)

Before: 305 usec spent in netstat_seq_show()
After: 130 usec spent in netstat_seq_show()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20210128162145.1703601-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 63cd370..6d46297 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -464,30 +464,52 @@ static int snmp_seq_show(struct seq_file *seq, void *v)
  */
 static int netstat_seq_show(struct seq_file *seq, void *v)
 {
-       int i;
+       const int ip_cnt = ARRAY_SIZE(snmp4_ipextstats_list) - 1;
+       const int tcp_cnt = ARRAY_SIZE(snmp4_net_list) - 1;
        struct net *net = seq->private;
+       unsigned long *buff;
+       int i;
 
        seq_puts(seq, "TcpExt:");
-       for (i = 0; snmp4_net_list[i].name; i++)
+       for (i = 0; i < tcp_cnt; i++)
                seq_printf(seq, " %s", snmp4_net_list[i].name);
 
        seq_puts(seq, "\nTcpExt:");
-       for (i = 0; snmp4_net_list[i].name; i++)
-               seq_printf(seq, " %lu",
-                          snmp_fold_field(net->mib.net_statistics,
-                                          snmp4_net_list[i].entry));
-
+       buff = kzalloc(max(tcp_cnt * sizeof(long), ip_cnt * sizeof(u64)),
+                      GFP_KERNEL);
+       if (buff) {
+               snmp_get_cpu_field_batch(buff, snmp4_net_list,
+                                        net->mib.net_statistics);
+               for (i = 0; i < tcp_cnt; i++)
+                       seq_printf(seq, " %lu", buff[i]);
+       } else {
+               for (i = 0; i < tcp_cnt; i++)
+                       seq_printf(seq, " %lu",
+                                  snmp_fold_field(net->mib.net_statistics,
+                                                  snmp4_net_list[i].entry));
+       }
        seq_puts(seq, "\nIpExt:");
-       for (i = 0; snmp4_ipextstats_list[i].name; i++)
+       for (i = 0; i < ip_cnt; i++)
                seq_printf(seq, " %s", snmp4_ipextstats_list[i].name);
 
        seq_puts(seq, "\nIpExt:");
-       for (i = 0; snmp4_ipextstats_list[i].name; i++)
-               seq_printf(seq, " %llu",
-                          snmp_fold_field64(net->mib.ip_statistics,
-                                            snmp4_ipextstats_list[i].entry,
-                                            offsetof(struct ipstats_mib, syncp)));
-
+       if (buff) {
+               u64 *buff64 = (u64 *)buff;
+
+               memset(buff64, 0, ip_cnt * sizeof(u64));
+               snmp_get_cpu_field64_batch(buff64, snmp4_ipextstats_list,
+                                          net->mib.ip_statistics,
+                                          offsetof(struct ipstats_mib, syncp));
+               for (i = 0; i < ip_cnt; i++)
+                       seq_printf(seq, " %llu", buff64[i]);
+       } else {
+               for (i = 0; i < ip_cnt; i++)
+                       seq_printf(seq, " %llu",
+                                  snmp_fold_field64(net->mib.ip_statistics,
+                                                    snmp4_ipextstats_list[i].entry,
+                                                    offsetof(struct ipstats_mib, syncp)));
+       }
+       kfree(buff);
        seq_putc(seq, '\n');
        mptcp_seq_show(seq);
        return 0;