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[PATCH v6 0/7] Reduce cache miss for snmp_fold_field

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  [PATCH v6 0/7] Reduce cache miss for snmp_fold_field Jia He <hejianet@gmail.com> - 2016-09-30 05:30 +0200
    [PATCH v6 4/7] proc: Reduce cache miss in sctp_snmp_seq_show Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    [PATCH v6 6/7] ipv6: Remove useless parameter in __snmp6_fill_statsdev Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    [PATCH v6 5/7] proc: Reduce cache miss in xfrm_statistics_seq_show Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    [PATCH v6 2/7] proc: Reduce cache miss in snmp_seq_show Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    [PATCH v6 1/7] net:snmp: Introduce generic interfaces for snmp_get_cpu_field{,64} Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    [PATCH v6 3/7] proc: Reduce cache miss in snmp6_seq_show Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    [PATCH v6 7/7] net: Suppress the "Comparison to NULL could be written" warnings Jia He <hejianet@gmail.com> - 2016-09-30 05:40 +0200
    Re: [PATCH v6 0/7] Reduce cache miss for snmp_fold_field David Miller <davem@davemloft.net> - 2016-09-30 08:20 +0200

#1493864 — [PATCH v6 0/7] Reduce cache miss for snmp_fold_field

In a PowerPc server with large cpu number(160), besides commit
a3a773726c9f ("net: Optimize snmp stat aggregation by walking all
the percpu data at once"), I watched several other snmp_fold_field
callsites which would cause high cache miss rate.

test source code:
================
My simple test case, which read from the procfs items endlessly:
/***********************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define LINELEN  2560
int main(int argc, char **argv)
{
        int i;
        int fd = -1 ;
        int rdsize = 0;
        char buf[LINELEN+1];

        buf[LINELEN] = 0;
        memset(buf,0,LINELEN);

        if(1 >= argc) {
                printf("file name empty\n");
                return -1;
        }

        fd = open(argv[1], O_RDWR, 0644);
        if(0 > fd){
                printf("open error\n");
                return -2;
        }

        for(i=0;i<0xffffffff;i++) {
                while(0 < (rdsize = read(fd,buf,LINELEN))){
                        //nothing here
                }

                lseek(fd, 0, SEEK_SET);
        }

        close(fd);
        return 0;
}
/**********************************************************/

compile and run:
================
gcc test.c -o test

perf stat -d -e cache-misses ./test /proc/net/snmp
perf stat -d -e cache-misses ./test /proc/net/snmp6
perf stat -d -e cache-misses ./test /proc/net/sctp/snmp
perf stat -d -e cache-misses ./test /proc/net/xfrm_stat

before the patch set:
====================
 Performance counter stats for 'system wide':

         355911097      cache-misses                                                 [40.08%]
        2356829300      L1-dcache-loads                                              [60.04%]
         355642645      L1-dcache-load-misses     #   15.09% of all L1-dcache hits   [60.02%]
         346544541      LLC-loads                                                    [59.97%]
            389763      LLC-load-misses           #    0.11% of all LL-cache hits    [40.02%]

       6.245162638 seconds time elapsed

After the patch set:
===================
 Performance counter stats for 'system wide':

         194992476      cache-misses                                                 [40.03%]
        6718051877      L1-dcache-loads                                              [60.07%]
         194871921      L1-dcache-load-misses     #    2.90% of all L1-dcache hits   [60.11%]
         187632232      LLC-loads                                                    [60.04%]
            464466      LLC-load-misses           #    0.25% of all LL-cache hits    [39.89%]

       6.868422769 seconds time elapsed
The cache-miss rate can be reduced from 15% to 2.9%

changelog
=========
v6:
- correct v5 
v5:
- order local variables from longest to shortest line
v4:
- move memset into one block of if statement in snmp6_seq_show_item
- remove the changes in netstat_seq_show considerred the stack usage is too large
v3:
- introduce generic interface (suggested by Marcelo Ricardo Leitner)
- use max_t instead of self defined macro (suggested by David Miller)
v2:
- fix bug in udplite statistics.
- snmp_seq_show is split into 2 parts

Jia He (7):
  net:snmp: Introduce generic interfaces for snmp_get_cpu_field{,64}
  proc: Reduce cache miss in snmp_seq_show
  proc: Reduce cache miss in snmp6_seq_show
  proc: Reduce cache miss in sctp_snmp_seq_show
  proc: Reduce cache miss in xfrm_statistics_seq_show
  ipv6: Remove useless parameter in __snmp6_fill_statsdev
  net: Suppress the "Comparison to NULL could be written" warnings

 include/net/ip.h     |  23 ++++++++++++
 net/ipv4/proc.c      | 102 +++++++++++++++++++++++++++++++--------------------
 net/ipv6/addrconf.c  |  12 +++---
 net/ipv6/proc.c      |  30 +++++++++++----
 net/sctp/proc.c      |  10 +++--
 net/xfrm/xfrm_proc.c |  10 ++++-
 6 files changed, 129 insertions(+), 58 deletions(-)

-- 
2.5.5

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#1493865 — [PATCH v6 4/7] proc: Reduce cache miss in sctp_snmp_seq_show

This is to use the generic interfaces 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/sctp/proc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/sctp/proc.c b/net/sctp/proc.c
index ef8ba77..09e16c2 100644
--- a/net/sctp/proc.c
+++ b/net/sctp/proc.c
@@ -73,13 +73,17 @@ static const struct snmp_mib sctp_snmp_list[] = {
 /* Display sctp snmp mib statistics(/proc/net/sctp/snmp). */
 static int sctp_snmp_seq_show(struct seq_file *seq, void *v)
 {
+	unsigned long buff[SCTP_MIB_MAX];
 	struct net *net = seq->private;
 	int i;
 
+	memset(buff, 0, sizeof(unsigned long) * SCTP_MIB_MAX);
+
+	snmp_get_cpu_field_batch(buff, sctp_snmp_list,
+				 net->sctp.sctp_statistics);
 	for (i = 0; sctp_snmp_list[i].name != NULL; i++)
 		seq_printf(seq, "%-32s\t%ld\n", sctp_snmp_list[i].name,
-			   snmp_fold_field(net->sctp.sctp_statistics,
-				      sctp_snmp_list[i].entry));
+						buff[i]);
 
 	return 0;
 }
-- 
2.5.5

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#1493866 — [PATCH v6 6/7] ipv6: Remove useless parameter in __snmp6_fill_statsdev

The parameter items(is always ICMP6_MIB_MAX) is useless for __snmp6_fill_statsdev

Signed-off-by: Jia He <hejianet@gmail.com>
---
 net/ipv6/addrconf.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 2f1f5d4..35d4baa 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4961,18 +4961,18 @@ static inline size_t inet6_if_nlmsg_size(void)
 }
 
 static inline void __snmp6_fill_statsdev(u64 *stats, atomic_long_t *mib,
-				      int items, int bytes)
+					int bytes)
 {
 	int i;
-	int pad = bytes - sizeof(u64) * items;
+	int pad = bytes - sizeof(u64) * ICMP6_MIB_MAX;
 	BUG_ON(pad < 0);
 
 	/* Use put_unaligned() because stats may not be aligned for u64. */
-	put_unaligned(items, &stats[0]);
-	for (i = 1; i < items; i++)
+	put_unaligned(ICMP6_MIB_MAX, &stats[0]);
+	for (i = 1; i < ICMP6_MIB_MAX; i++)
 		put_unaligned(atomic_long_read(&mib[i]), &stats[i]);
 
-	memset(&stats[items], 0, pad);
+	memset(&stats[ICMP6_MIB_MAX], 0, pad);
 }
 
 static inline void __snmp6_fill_stats64(u64 *stats, void __percpu *mib,
@@ -5005,7 +5005,7 @@ static void snmp6_fill_stats(u64 *stats, struct inet6_dev *idev, int attrtype,
 				     offsetof(struct ipstats_mib, syncp));
 		break;
 	case IFLA_INET6_ICMP6STATS:
-		__snmp6_fill_statsdev(stats, idev->stats.icmpv6dev->mibs, ICMP6_MIB_MAX, bytes);
+		__snmp6_fill_statsdev(stats, idev->stats.icmpv6dev->mibs, bytes);
 		break;
 	}
 }
-- 
2.5.5

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#1493867 — [PATCH v6 5/7] proc: Reduce cache miss in xfrm_statistics_seq_show

This is to use the generic interfaces 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/xfrm/xfrm_proc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_proc.c b/net/xfrm/xfrm_proc.c
index 9c4fbd8..ba2b539 100644
--- a/net/xfrm/xfrm_proc.c
+++ b/net/xfrm/xfrm_proc.c
@@ -50,12 +50,18 @@ static const struct snmp_mib xfrm_mib_list[] = {
 
 static int xfrm_statistics_seq_show(struct seq_file *seq, void *v)
 {
+	unsigned long buff[LINUX_MIB_XFRMMAX];
 	struct net *net = seq->private;
 	int i;
+
+	memset(buff, 0, sizeof(unsigned long) * LINUX_MIB_XFRMMAX);
+
+	snmp_get_cpu_field_batch(buff, xfrm_mib_list,
+				 net->mib.xfrm_statistics);
 	for (i = 0; xfrm_mib_list[i].name; i++)
 		seq_printf(seq, "%-24s\t%lu\n", xfrm_mib_list[i].name,
-			   snmp_fold_field(net->mib.xfrm_statistics,
-					   xfrm_mib_list[i].entry));
+						buff[i]);
+
 	return 0;
 }
 
-- 
2.5.5

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#1493869 — [PATCH v6 2/7] proc: Reduce cache miss in snmp_seq_show

This is to use the generic interfaces snmp_get_cpu_field{,64}_batch to
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 | 70 ++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 47 insertions(+), 23 deletions(-)

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 9f665b6..9d7a39a 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -46,6 +46,8 @@
 #include <net/sock.h>
 #include <net/raw.h>
 
+#define TCPUDP_MIB_MAX max_t(u32, UDP_MIB_MAX, TCP_MIB_MAX)
+
 /*
  *	Report socket allocation statistics [mea@utu.fi]
  */
@@ -378,13 +380,15 @@ 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;
 	struct net *net = seq->private;
+	u64 buff64[IPSTATS_MIB_MAX];
+	int i;
 
-	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 +397,77 @@ 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);
+	snmp_get_cpu_field64_batch(buff64, snmp4_ipstats_list,
+				   net->mib.ip_statistics,
+				   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)
+{
+	unsigned long buff[TCPUDP_MIB_MAX];
+	struct net *net = seq->private;
+	int i;
+
+	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:");
+	snmp_get_cpu_field_batch(buff, snmp4_tcp_list,
+				 net->mib.tcp_statistics);
 	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));
+
+	snmp_get_cpu_field_batch(buff, snmp4_udp_list,
+				 net->mib.udp_statistics);
 	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:");
+	snmp_get_cpu_field_batch(buff, snmp4_udp_list,
+				 net->mib.udplite_statistics);
 	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);
-- 
2.5.5

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#1493871 — [PATCH v6 1/7] net:snmp: Introduce generic interfaces for snmp_get_cpu_field{,64}

This is to introduce the generic interfaces for snmp_get_cpu_field{,64}.
It exchanges the two for-loops for collecting the percpu statistics data.
This can aggregate the data by going through all the items of each cpu
sequentially.

Signed-off-by: Jia He <hejianet@gmail.com>
Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
 include/net/ip.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/net/ip.h b/include/net/ip.h
index 9742b92..bc43c0f 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -219,6 +219,29 @@ static inline u64 snmp_fold_field64(void __percpu *mib, int offt, size_t syncp_o
 }
 #endif
 
+#define snmp_get_cpu_field64_batch(buff64, stats_list, mib_statistic, offset) \
+{ \
+	int i, c; \
+	for_each_possible_cpu(c) { \
+		for (i = 0; stats_list[i].name; i++) \
+			buff64[i] += snmp_get_cpu_field64( \
+					mib_statistic, \
+					c, stats_list[i].entry, \
+					offset); \
+	} \
+}
+
+#define snmp_get_cpu_field_batch(buff, stats_list, mib_statistic) \
+{ \
+	int i, c; \
+	for_each_possible_cpu(c) { \
+		for (i = 0; stats_list[i].name; i++) \
+			buff[i] += snmp_get_cpu_field( \
+						mib_statistic, \
+						c, stats_list[i].entry); \
+	} \
+}
+
 void inet_get_local_port_range(struct net *net, int *low, int *high);
 
 #ifdef CONFIG_SYSCTL
-- 
2.5.5

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#1493873 — [PATCH v6 3/7] proc: Reduce cache miss in snmp6_seq_show

This is to use the generic interfaces 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 | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index 679253d0..cc8e3ae 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;
@@ -191,25 +196,34 @@ static void snmp6_seq_show_item(struct seq_file *seq, void __percpu *pcpumib,
 				atomic_long_t *smib,
 				const struct snmp_mib *itemlist)
 {
+	unsigned long buff[SNMP_MIB_MAX];
 	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);
+	if (pcpumib) {
+		memset(buff, 0, sizeof(unsigned long) * SNMP_MIB_MAX);
+
+		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));
 	}
 }
 
 static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu *mib,
 				  const struct snmp_mib *itemlist, size_t syncpoff)
 {
+	u64 buff64[SNMP_MIB_MAX];
 	int i;
 
+	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)
-- 
2.5.5

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#1493874 — [PATCH v6 7/7] net: Suppress the "Comparison to NULL could be written" warnings

This is to suppress the checkpatch.pl warning "Comparison to NULL
could be written". No functional changes here.

Signed-off-by: Jia He <hejianet@gmail.com>
---
 net/ipv4/proc.c | 32 ++++++++++++++++----------------
 net/sctp/proc.c |  2 +-
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 9d7a39a..b39faf6 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -357,22 +357,22 @@ static void icmp_put(struct seq_file *seq)
 	atomic_long_t *ptr = net->mib.icmpmsg_statistics->mibs;
 
 	seq_puts(seq, "\nIcmp: InMsgs InErrors InCsumErrors");
-	for (i = 0; icmpmibmap[i].name != NULL; i++)
+	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " In%s", icmpmibmap[i].name);
 	seq_puts(seq, " OutMsgs OutErrors");
-	for (i = 0; icmpmibmap[i].name != NULL; i++)
+	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " Out%s", icmpmibmap[i].name);
 	seq_printf(seq, "\nIcmp: %lu %lu %lu",
 		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_INMSGS),
 		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_INERRORS),
 		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_CSUMERRORS));
-	for (i = 0; icmpmibmap[i].name != NULL; i++)
+	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " %lu",
 			   atomic_long_read(ptr + icmpmibmap[i].index));
 	seq_printf(seq, " %lu %lu",
 		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_OUTMSGS),
 		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_OUTERRORS));
-	for (i = 0; icmpmibmap[i].name != NULL; i++)
+	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " %lu",
 			   atomic_long_read(ptr + (icmpmibmap[i].index | 0x100)));
 }
@@ -389,7 +389,7 @@ static int snmp_seq_show_ipstats(struct seq_file *seq, void *v)
 	memset(buff64, 0, IPSTATS_MIB_MAX * sizeof(u64));
 
 	seq_puts(seq, "Ip: Forwarding DefaultTTL");
-	for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
+	for (i = 0; snmp4_ipstats_list[i].name; i++)
 		seq_printf(seq, " %s", snmp4_ipstats_list[i].name);
 
 	seq_printf(seq, "\nIp: %d %d",
@@ -400,7 +400,7 @@ static int snmp_seq_show_ipstats(struct seq_file *seq, void *v)
 	snmp_get_cpu_field64_batch(buff64, snmp4_ipstats_list,
 				   net->mib.ip_statistics,
 				   offsetof(struct ipstats_mib, syncp));
-	for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
+	for (i = 0; snmp4_ipstats_list[i].name; i++)
 		seq_printf(seq, " %llu", buff64[i]);
 
 	return 0;
@@ -415,13 +415,13 @@ static int snmp_seq_show_tcp_udp(struct seq_file *seq, void *v)
 	memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));
 
 	seq_puts(seq, "\nTcp:");
-	for (i = 0; snmp4_tcp_list[i].name != NULL; i++)
+	for (i = 0; snmp4_tcp_list[i].name; i++)
 		seq_printf(seq, " %s", snmp4_tcp_list[i].name);
 
 	seq_puts(seq, "\nTcp:");
 	snmp_get_cpu_field_batch(buff, snmp4_tcp_list,
 				 net->mib.tcp_statistics);
-	for (i = 0; snmp4_tcp_list[i].name != NULL; i++) {
+	for (i = 0; snmp4_tcp_list[i].name; i++) {
 		/* MaxConn field is signed, RFC 2012 */
 		if (snmp4_tcp_list[i].entry == TCP_MIB_MAXCONN)
 			seq_printf(seq, " %ld", buff[i]);
@@ -434,10 +434,10 @@ static int snmp_seq_show_tcp_udp(struct seq_file *seq, void *v)
 	snmp_get_cpu_field_batch(buff, snmp4_udp_list,
 				 net->mib.udp_statistics);
 	seq_puts(seq, "\nUdp:");
-	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
+	for (i = 0; snmp4_udp_list[i].name; i++)
 		seq_printf(seq, " %s", snmp4_udp_list[i].name);
 	seq_puts(seq, "\nUdp:");
-	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
+	for (i = 0; snmp4_udp_list[i].name; i++)
 		seq_printf(seq, " %lu", buff[i]);
 
 	memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));
@@ -446,10 +446,10 @@ static int snmp_seq_show_tcp_udp(struct seq_file *seq, void *v)
 	seq_puts(seq, "\nUdpLite:");
 	snmp_get_cpu_field_batch(buff, snmp4_udp_list,
 				 net->mib.udplite_statistics);
-	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
+	for (i = 0; snmp4_udp_list[i].name; i++)
 		seq_printf(seq, " %s", snmp4_udp_list[i].name);
 	seq_puts(seq, "\nUdpLite:");
-	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
+	for (i = 0; snmp4_udp_list[i].name; i++)
 		seq_printf(seq, " %lu", buff[i]);
 
 	seq_putc(seq, '\n');
@@ -492,21 +492,21 @@ static int netstat_seq_show(struct seq_file *seq, void *v)
 	struct net *net = seq->private;
 
 	seq_puts(seq, "TcpExt:");
-	for (i = 0; snmp4_net_list[i].name != NULL; i++)
+	for (i = 0; snmp4_net_list[i].name; i++)
 		seq_printf(seq, " %s", snmp4_net_list[i].name);
 
 	seq_puts(seq, "\nTcpExt:");
-	for (i = 0; snmp4_net_list[i].name != NULL; i++)
+	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));
 
 	seq_puts(seq, "\nIpExt:");
-	for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
+	for (i = 0; snmp4_ipextstats_list[i].name; i++)
 		seq_printf(seq, " %s", snmp4_ipextstats_list[i].name);
 
 	seq_puts(seq, "\nIpExt:");
-	for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
+	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,
diff --git a/net/sctp/proc.c b/net/sctp/proc.c
index 09e16c2..206377f 100644
--- a/net/sctp/proc.c
+++ b/net/sctp/proc.c
@@ -81,7 +81,7 @@ static int sctp_snmp_seq_show(struct seq_file *seq, void *v)
 
 	snmp_get_cpu_field_batch(buff, sctp_snmp_list,
 				 net->sctp.sctp_statistics);
-	for (i = 0; sctp_snmp_list[i].name != NULL; i++)
+	for (i = 0; sctp_snmp_list[i].name; i++)
 		seq_printf(seq, "%-32s\t%ld\n", sctp_snmp_list[i].name,
 						buff[i]);
 
-- 
2.5.5

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#1493904

From: Jia He <hejianet@gmail.com>
Date: Fri, 30 Sep 2016 11:28:57 +0800

> In a PowerPc server with large cpu number(160), besides commit
> a3a773726c9f ("net: Optimize snmp stat aggregation by walking all
> the percpu data at once"), I watched several other snmp_fold_field
> callsites which would cause high cache miss rate.
 ...

Series applied, thank you.

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