Merge branch 'net_proc_perf'

Jia He says:

====================
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:
/***********************************************************/
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
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 0 deletions

diff --git a/include/net/ip.h b/include/net/ip.h
index 9742b92dc933..bc43c0fcae12 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