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ipv6: reduce percpu needs for icmpv6msg mibs

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Reading /proc/net/snmp6 on a machine with a lot of cpus is very
expensive (can be ~88000 us).

This is because ICMPV6MSG MIB uses 4096 bytes per cpu, and folding
values for all possible cpus can read 16 Mbytes of memory (32MBytes on
non x86 arches)

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>
This commit is contained in:
Eric Dumazet
2011-11-13 01:24:04 +00:00
committed by David S. Miller
parent 3d249d4ca7
commit 2a24444f8f
5 changed files with 23 additions and 19 deletions
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2
include/net/snmp.h
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@@ -84,7 +84,7 @@ struct icmpv6_mib_device {
#define ICMP6MSG_MIB_MAX __ICMP6MSG_MIB_MAX
/* per network ns counters */
struct icmpv6msg_mib {
unsigned long mibs[ICMP6MSG_MIB_MAX];
atomic_long_t mibs[ICMP6MSG_MIB_MAX];
};
/* per device counters, (shared on all cpus) */
struct icmpv6msg_mib_device {