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This is a patch to provide on demand route cache rebuilding. Currently, our route cache is rebulid periodically regardless of need. This introduced unneeded periodic latency. This patch offers a better approach. Using code provided by Eric Dumazet, we compute the standard deviation of the average hash bucket chain length while running rt_check_expire. Should any given chain length grow to larger that average plus 4 standard deviations, we trigger an emergency hash table rebuild for that net namespace. This allows for the common case in which chains are well behaved and do not grow unevenly to not incur any latency at all, while those systems (which may be being maliciously attacked), only rebuild when the attack is detected. This patch take 2 other factors into account: 1) chains with multiple entries that differ by attributes that do not affect the hash value are only counted once, so as not to unduly bias system to rebuilding if features like QOS are heavily used 2) if rebuilding crosses a certain threshold (which is adjustable via the added sysctl in this patch), route caching is disabled entirely for that net namespace, since constant rebuilding is less efficient that no caching at all Tested successfully by me. Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| .. | ||
| conntrack.h | ||
| core.h | ||
| dccp.h | ||
| generic.h | ||
| hash.h | ||
| ipv4.h | ||
| ipv6.h | ||
| mib.h | ||
| packet.h | ||
| unix.h | ||
| x_tables.h | ||