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ipv4: reduce percpu needs for icmpmsg mibs
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Reading /proc/net/snmp on a machine with a lot of cpus is very expensive
(can be ~88000 us).

This is because ICMPMSG MIB uses 4096 bytes per cpu, and folding values
for all possible cpus can read 16 Mbytes of memory.

ICMP messages are not considered as fast path on a typical server, and
eventually few cpus handle them anyway. We can afford an atomic
operation instead of using percpu data.

This saves 4096 bytes per cpu and per network namespace.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Nov 9, 2011
1 parent e56c57d commit acb32ba
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Showing 5 changed files with 12 additions and 13 deletions.
4 changes: 2 additions & 2 deletions include/net/icmp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,8 +31,8 @@ struct icmp_err {
extern const struct icmp_err icmp_err_convert[];
#define ICMP_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.icmp_statistics, field)
#define ICMP_INC_STATS_BH(net, field) SNMP_INC_STATS_BH((net)->mib.icmp_statistics, field)
#define ICMPMSGOUT_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.icmpmsg_statistics, field+256)
#define ICMPMSGIN_INC_STATS_BH(net, field) SNMP_INC_STATS_BH((net)->mib.icmpmsg_statistics, field)
#define ICMPMSGOUT_INC_STATS(net, field) SNMP_INC_STATS_ATOMIC_LONG((net)->mib.icmpmsg_statistics, field+256)
#define ICMPMSGIN_INC_STATS_BH(net, field) SNMP_INC_STATS_ATOMIC_LONG((net)->mib.icmpmsg_statistics, field)

struct dst_entry;
struct net_proto_family;
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2 changes: 1 addition & 1 deletion include/net/netns/mib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ struct netns_mib {
DEFINE_SNMP_STAT(struct udp_mib, udp_statistics);
DEFINE_SNMP_STAT(struct udp_mib, udplite_statistics);
DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics);
DEFINE_SNMP_STAT(struct icmpmsg_mib, icmpmsg_statistics);
DEFINE_SNMP_STAT_ATOMIC(struct icmpmsg_mib, icmpmsg_statistics);

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
struct proc_dir_entry *proc_net_devsnmp6;
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2 changes: 1 addition & 1 deletion include/net/snmp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ struct icmp_mib {

#define ICMPMSG_MIB_MAX __ICMPMSG_MIB_MAX
struct icmpmsg_mib {
unsigned long mibs[ICMPMSG_MIB_MAX];
atomic_long_t mibs[ICMPMSG_MIB_MAX];
};

/* ICMP6 (IPv6-ICMP) */
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8 changes: 4 additions & 4 deletions net/ipv4/af_inet.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1572,9 +1572,9 @@ static __net_init int ipv4_mib_init_net(struct net *net)
sizeof(struct icmp_mib),
__alignof__(struct icmp_mib)) < 0)
goto err_icmp_mib;
if (snmp_mib_init((void __percpu **)net->mib.icmpmsg_statistics,
sizeof(struct icmpmsg_mib),
__alignof__(struct icmpmsg_mib)) < 0)
net->mib.icmpmsg_statistics = kzalloc(sizeof(struct icmpmsg_mib),
GFP_KERNEL);
if (!net->mib.icmpmsg_statistics)
goto err_icmpmsg_mib;

tcp_mib_init(net);
Expand All @@ -1598,7 +1598,7 @@ static __net_init int ipv4_mib_init_net(struct net *net)

static __net_exit void ipv4_mib_exit_net(struct net *net)
{
snmp_mib_free((void __percpu **)net->mib.icmpmsg_statistics);
kfree(net->mib.icmpmsg_statistics);
snmp_mib_free((void __percpu **)net->mib.icmp_statistics);
snmp_mib_free((void __percpu **)net->mib.udplite_statistics);
snmp_mib_free((void __percpu **)net->mib.udp_statistics);
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9 changes: 4 additions & 5 deletions net/ipv4/proc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -288,7 +288,7 @@ static void icmpmsg_put(struct seq_file *seq)

count = 0;
for (i = 0; i < ICMPMSG_MIB_MAX; i++) {
val = snmp_fold_field((void __percpu **) net->mib.icmpmsg_statistics, i);
val = atomic_long_read(&net->mib.icmpmsg_statistics->mibs[i]);
if (val) {
type[count] = i;
vals[count++] = val;
Expand All @@ -307,6 +307,7 @@ static void icmp_put(struct seq_file *seq)
{
int i;
struct net *net = seq->private;
atomic_long_t *ptr = net->mib.icmpmsg_statistics->mibs;

seq_puts(seq, "\nIcmp: InMsgs InErrors");
for (i=0; icmpmibmap[i].name != NULL; i++)
Expand All @@ -319,15 +320,13 @@ static void icmp_put(struct seq_file *seq)
snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_INERRORS));
for (i=0; icmpmibmap[i].name != NULL; i++)
seq_printf(seq, " %lu",
snmp_fold_field((void __percpu **) net->mib.icmpmsg_statistics,
icmpmibmap[i].index));
atomic_long_read(ptr + icmpmibmap[i].index));
seq_printf(seq, " %lu %lu",
snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_OUTMSGS),
snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_OUTERRORS));
for (i=0; icmpmibmap[i].name != NULL; i++)
seq_printf(seq, " %lu",
snmp_fold_field((void __percpu **) net->mib.icmpmsg_statistics,
icmpmibmap[i].index | 0x100));
atomic_long_read(ptr + (icmpmibmap[i].index | 0x100)));
}

/*
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