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    Subject8-CPU (SMP) #s for lockfree rtcache
    Hi Dave,

    Here are the SMP numbers that you had asked for. They were measured
    on an 8-CPU SMP box (PIII Xeon 700 MHz processors, 1MB L2 cache
    and 6GB RAM).

    The test was as per your suggestion. rt_rcu is a patch that
    uses RCU to do lockfree lookup of ipv4 route cache.

    The basic test sends a fixed number of packets to random
    destination addresses repeating every dest for 5 packets.
    We tried two configurations of this test - 8-1-32 where
    32 test processes simultaneosly uses 32 different
    random seeds to generate different dest addreses and 8-4-8
    where 8 sets, each consisting 4 processes all of whom use the same
    random seed generating the same dst addresses, send packets
    to the dest addresses repeating dest for every 5 packets.

    With these basic tests, we measured under several other
    conditions - avoid forced neighbor table garbage collection
    by increasing the threshold and interval (to 31048576 and
    60) and slowing the packet rate by introducing a delay of 2ms
    between bursts of 5 packets.

    Here are the results in terms of profile counts in
    ip_route_output_key() - gc stands for neighbor table garbage
    collection adjustment and u2000 stands for 2ms packet
    rate delay. All measurements where done based on 2.5.3 kernel.

    Test base rtrcu speedup
    ---- ---- ----- -------
    8-1-32 2358 1655 29.8%
    8-1-32-gc 4486 2176 51.4%
    8-1-32-u2000 2990 1942 35.0%
    8-1-32-u2000-gc 4047 2029 49.8%

    8-4-8 2870 1965 31.5%
    8-4-8-gc 3389 2083 38.5%
    8-4-8-u2000 3459 2373 31.3%
    8-4-8-u2000-gc 4686 2603 44.4%

    Dipankar Sarma <>
    Linux Technology Center, IBM Software Lab, Bangalore, India.
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