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authorAnton Blanchard <anton@samba.org>2009-04-27 05:42:24 -0700
committerDavid S. Miller <davem@davemloft.net>2009-04-27 05:42:24 -0700
commitc9503e0fe052020e0294cd07d0ecd982eb7c9177 (patch)
treeaa0425fc1f30ebdf8d7455cf59db5c3ea2c7dfd0 /include
parent2296e5a0136f7ba64c99f3a48a55a687aa9abcc8 (diff)
ipv4: Limit size of route cache hash table
Right now we have no upper limit on the size of the route cache hash table. On a 128GB POWER6 box it ends up as 32MB: IP route cache hash table entries: 4194304 (order: 9, 33554432 bytes) It would be nice to cap this for memory consumption reasons, but a massive hashtable also causes a significant spike when measuring OS jitter. With a 32MB hashtable and 4 million entries, rt_worker_func is taking 5 ms to complete. On another system with more memory it's taking 14 ms. Even though rt_worker_func does call cond_sched() to limit its impact, in an HPC environment we want to keep all sources of OS jitter to a minimum. With the patch applied we limit the number of entries to 512k which can still be overriden by using the rt_entries boot option: IP route cache hash table entries: 524288 (order: 6, 4194304 bytes) With this patch rt_worker_func now takes 0.460 ms on the same system. Signed-off-by: Anton Blanchard <anton@samba.org> Acked-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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