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Subject[RFC PATCH v2 1/6] proc: Reduce cache miss in {snmp,netstat}_seq_show
Date
This patch exchanges the two loop for collecting the percpu statistics
data. This can aggregate the data by going through all the items of each
cpu sequentially. Then snmp_seq_show is split into 2 parts to avoid build
warning "the frame size" larger than 1024.

Signed-off-by: Jia He <hejianet@gmail.com>
---
net/ipv4/proc.c | 112 ++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 81 insertions(+), 31 deletions(-)

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 9f665b6..f413fdc 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -46,6 +46,9 @@
#include <net/sock.h>
#include <net/raw.h>

+#define MAX(a, b) ((u32)(a) >= (u32)(b) ? (a) : (b))
+#define TCPUDP_MIB_MAX MAX(UDP_MIB_MAX, TCP_MIB_MAX)
+
/*
* Report socket allocation statistics [mea@utu.fi]
*/
@@ -378,13 +381,15 @@ static void icmp_put(struct seq_file *seq)
/*
* Called from the PROCfs module. This outputs /proc/net/snmp.
*/
-static int snmp_seq_show(struct seq_file *seq, void *v)
+static int snmp_seq_show_ipstats(struct seq_file *seq, void *v)
{
- int i;
+ int i, c;
+ u64 buff64[IPSTATS_MIB_MAX];
struct net *net = seq->private;

- seq_puts(seq, "Ip: Forwarding DefaultTTL");
+ memset(buff64, 0, IPSTATS_MIB_MAX * sizeof(u64));

+ seq_puts(seq, "Ip: Forwarding DefaultTTL");
for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
seq_printf(seq, " %s", snmp4_ipstats_list[i].name);

@@ -393,57 +398,92 @@ static int snmp_seq_show(struct seq_file *seq, void *v)
net->ipv4.sysctl_ip_default_ttl);

BUILD_BUG_ON(offsetof(struct ipstats_mib, mibs) != 0);
+
+ for_each_possible_cpu(c) {
+ for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
+ buff64[i] += snmp_get_cpu_field64(
+ net->mib.ip_statistics,
+ c, snmp4_ipstats_list[i].entry,
+ offsetof(struct ipstats_mib, syncp));
+ }
for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
- seq_printf(seq, " %llu",
- snmp_fold_field64(net->mib.ip_statistics,
- snmp4_ipstats_list[i].entry,
- offsetof(struct ipstats_mib, syncp)));
+ seq_printf(seq, " %llu", buff64[i]);

- icmp_put(seq); /* RFC 2011 compatibility */
- icmpmsg_put(seq);
+ return 0;
+}
+
+static int snmp_seq_show_tcp_udp(struct seq_file *seq, void *v)
+{
+ int i, c;
+ unsigned long buff[TCPUDP_MIB_MAX];
+ struct net *net = seq->private;
+
+ memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));

seq_puts(seq, "\nTcp:");
for (i = 0; snmp4_tcp_list[i].name != NULL; i++)
seq_printf(seq, " %s", snmp4_tcp_list[i].name);

seq_puts(seq, "\nTcp:");
+ for_each_possible_cpu(c) {
+ for (i = 0; snmp4_tcp_list[i].name != NULL; i++)
+ buff[i] += snmp_get_cpu_field(net->mib.tcp_statistics,
+ c, snmp4_tcp_list[i].entry);
+ }
+
for (i = 0; snmp4_tcp_list[i].name != NULL; i++) {
/* MaxConn field is signed, RFC 2012 */
if (snmp4_tcp_list[i].entry == TCP_MIB_MAXCONN)
- seq_printf(seq, " %ld",
- snmp_fold_field(net->mib.tcp_statistics,
- snmp4_tcp_list[i].entry));
+ seq_printf(seq, " %ld", buff[i]);
else
- seq_printf(seq, " %lu",
- snmp_fold_field(net->mib.tcp_statistics,
- snmp4_tcp_list[i].entry));
+ seq_printf(seq, " %lu", buff[i]);
}

+ memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));
+
+ for_each_possible_cpu(c) {
+ for (i = 0; snmp4_udp_list[i].name != NULL; i++)
+ buff[i] += snmp_get_cpu_field(net->mib.udp_statistics,
+ c, snmp4_udp_list[i].entry);
+ }
seq_puts(seq, "\nUdp:");
for (i = 0; snmp4_udp_list[i].name != NULL; i++)
seq_printf(seq, " %s", snmp4_udp_list[i].name);
-
seq_puts(seq, "\nUdp:");
for (i = 0; snmp4_udp_list[i].name != NULL; i++)
- seq_printf(seq, " %lu",
- snmp_fold_field(net->mib.udp_statistics,
- snmp4_udp_list[i].entry));
+ seq_printf(seq, " %lu", buff[i]);
+
+ memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));

/* the UDP and UDP-Lite MIBs are the same */
seq_puts(seq, "\nUdpLite:");
+ for_each_possible_cpu(c) {
+ for (i = 0; snmp4_udp_list[i].name != NULL; i++)
+ buff[i] += snmp_get_cpu_field(net->mib.udplite_statistics,
+ c, snmp4_udp_list[i].entry);
+ }
for (i = 0; snmp4_udp_list[i].name != NULL; i++)
seq_printf(seq, " %s", snmp4_udp_list[i].name);
-
seq_puts(seq, "\nUdpLite:");
for (i = 0; snmp4_udp_list[i].name != NULL; i++)
- seq_printf(seq, " %lu",
- snmp_fold_field(net->mib.udplite_statistics,
- snmp4_udp_list[i].entry));
+ seq_printf(seq, " %lu", buff[i]);

seq_putc(seq, '\n');
return 0;
}

+static int snmp_seq_show(struct seq_file *seq, void *v)
+{
+ snmp_seq_show_ipstats(seq, v);
+
+ icmp_put(seq); /* RFC 2011 compatibility */
+ icmpmsg_put(seq);
+
+ snmp_seq_show_tcp_udp(seq, v);
+
+ return 0;
+}
+
static int snmp_seq_open(struct inode *inode, struct file *file)
{
return single_open_net(inode, file, snmp_seq_show);
@@ -464,29 +504,39 @@ static const struct file_operations snmp_seq_fops = {
*/
static int netstat_seq_show(struct seq_file *seq, void *v)
{
- int i;
+ int i, c;
+ unsigned long buff[LINUX_MIB_MAX];
+ u64 buff64[IPSTATS_MIB_MAX];
struct net *net = seq->private;

+ memset(buff, 0, sizeof(unsigned long) * LINUX_MIB_MAX);
+ memset(buff64, 0, sizeof(u64) * IPSTATS_MIB_MAX);
+
seq_puts(seq, "TcpExt:");
for (i = 0; snmp4_net_list[i].name != NULL; i++)
seq_printf(seq, " %s", snmp4_net_list[i].name);

seq_puts(seq, "\nTcpExt:");
+ for_each_possible_cpu(c)
+ for (i = 0; snmp4_net_list[i].name != NULL; i++)
+ buff[i] += snmp_get_cpu_field(net->mib.net_statistics,
+ c, snmp4_net_list[i].entry);
for (i = 0; snmp4_net_list[i].name != NULL; i++)
- seq_printf(seq, " %lu",
- snmp_fold_field(net->mib.net_statistics,
- snmp4_net_list[i].entry));
+ seq_printf(seq, " %lu", buff[i]);

seq_puts(seq, "\nIpExt:");
for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
seq_printf(seq, " %s", snmp4_ipextstats_list[i].name);

seq_puts(seq, "\nIpExt:");
+ for_each_possible_cpu(c)
+ for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
+ buff64[i] += snmp_get_cpu_field64(
+ net->mib.ip_statistics,
+ c, snmp4_ipextstats_list[i].entry,
+ offsetof(struct ipstats_mib, syncp));
for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
- seq_printf(seq, " %llu",
- snmp_fold_field64(net->mib.ip_statistics,
- snmp4_ipextstats_list[i].entry,
- offsetof(struct ipstats_mib, syncp)));
+ seq_printf(seq, " %llu", buff64[i]);

seq_putc(seq, '\n');
return 0;
--
1.8.3.1
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