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neigh: Keep neighbour cache entries if number of them is small enough.

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Since we have removed NCE (Neighbour Cache Entry) reference from
routing entries, the only refcnt holders of an NCE are its timer
(if running) and its owner table, in usual cases.  As a result,
neigh_periodic_work() purges NCEs over and over again even for
gateways.

It does not make sense to purge entries, if number of them is
very small, so keep them.  The minimum number of entries to keep
is specified by gc_thresh1.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
YOSHIFUJI Hideaki / 吉藤英明 2013-01-22 05:20:05 +00:00 committed by David S. Miller
parent 360eb5da66
commit 2724680bce
2 changed files with 9 additions and 0 deletions
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5
Documentation/networking/ip-sysctl.txt
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@ -26,6 +26,11 @@ route/max_size - INTEGER
Maximum number of routes allowed in the kernel. Increase
this when using large numbers of interfaces and/or routes.
neigh/default/gc_thresh1 - INTEGER
Minimum number of entries to keep. Garbage collector will not
purge entries if there are fewer than this number.
Default: 256
neigh/default/gc_thresh3 - INTEGER
Maximum number of neighbor entries allowed. Increase this
when using large numbers of interfaces and when communicating

4
net/core/neighbour.c
View File

@ -778,6 +778,9 @@ static void neigh_periodic_work(struct work_struct *work)
nht = rcu_dereference_protected(tbl->nht,
lockdep_is_held(&tbl->lock));
if (atomic_read(&tbl->entries) < tbl->gc_thresh1)
goto out;
/*
* periodically recompute ReachableTime from random function
*/
@ -832,6 +835,7 @@ static void neigh_periodic_work(struct work_struct *work)
nht = rcu_dereference_protected(tbl->nht,
lockdep_is_held(&tbl->lock));
}
out:
/* Cycle through all hash buckets every base_reachable_time/2 ticks.
* ARP entry timeouts range from 1/2 base_reachable_time to 3/2
* base_reachable_time.