Re: [PATCH] lockfree rtcache lookup using RCU

[Dipankar Sarma <dipankar@in.ibm.com>]

On Wed, May 08, 2002 at 06:45:28AM -0700, David S. Miller wrote:
>    From: Dipankar Sarma <dipankar@in.ibm.com>
>    Date: Wed, 8 May 2002 18:54:57 +0530
>    
>    A large number of processes of which small sets may look up the same
>    ip address. dst ip addresses change after every 50 packets or
>    so.
>    
>    Is this more realistic ?
> 
> More like every 4 or 5 packets.

Ok, here are some results from a test like that on a 8-way PIII
xeon with 1MB L2 cache. The test has 32 processes sending
random sized packets with dst ip changing every 5 packets.
There results are probably a bit skewed because of the neighbor
table overflows as seen in by the high profile count in
__write_lock_failed and neigh_forced_gc. It does seem that
the packet rate in this test is very high.

ip_route_output_key() is 22% faster with rt_rcu. I will publish 
the results on a 16way NUMA later.

Thanks
-- 
Dipankar Sarma  <dipankar@in.ibm.com> http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.



base (2.5.3)
----
__write_lock_failed [c0107af0]: 602749
stext_lock [c024eb18]: 178874
neigh_forced_gc [c020a430]: 104295
USER [c01263d0]: 49856
qdisc_restart [c020f070]: 45435
__read_lock_failed [c0107b10]: 35868
dev_queue_xmit [c0207d00]: 27545
__generic_copy_from_user [c0193b10]: 18680
ace_start_xmit [c01bf670]: 14331
nf_hook_slow [c020e940]: 8365
__kfree_skb [c0204180]: 6919
default_idle [c0106ed0]: 6511
sock_alloc_send_pskb [c02032d0]: 6420
ace_interrupt [c01bf180]: 6254
pfifo_fast_dequeue [c020f550]: 4466
net_tx_action [c0208230]: 4228
ip_finish_output2 [c0219520]: 3747
kfree_skbmem [c0204110]: 3436
ip_route_output_key [c0214470]: 3034



rt_rcu (2.5.3)
-------

__write_lock_failed [c0107af0]: 558354
stext_lock [c024ef58]: 227526
neigh_forced_gc [c020aaa0]: 100893
USER [c0126a40]: 49559
qdisc_restart [c020f6e0]: 45950
dev_queue_xmit [c0208370]: 27353
__read_lock_failed [c0107b10]: 24113
__generic_copy_from_user [c0194180]: 18375
ace_start_xmit [c01bfce0]: 15677
nf_hook_slow [c020efb0]: 8865
__kfree_skb [c02047f0]: 6890
sock_alloc_send_pskb [c0203940]: 6239
ace_interrupt [c01bf7f0]: 5982
default_idle [c0106ed0]: 4679
pfifo_fast_dequeue [c020fbc0]: 4067
ip_finish_output2 [c0219940]: 3886
kfree_skbmem [c0204780]: 3496 
pfifo_fast_enqueue [c020fb40]: 3003
net_tx_action [c02088a0]: 2994
sock_def_write_space [c0204230]: 2552
sock_wfree [c0203700]: 2408
skb_release_data [c02046f0]: 2395
ip_route_output_key [c0214990]: 2358