• Eric Dumazet's avatar
    net dst: use a percpu_counter to track entries · fc66f95c
    Eric Dumazet authored
    struct dst_ops tracks number of allocated dst in an atomic_t field,
    subject to high cache line contention in stress workload.
    
    Switch to a percpu_counter, to reduce number of time we need to dirty a
    central location. Place it on a separate cache line to avoid dirtying
    read only fields.
    
    Stress test :
    
    (Sending 160.000.000 UDP frames,
    IP route cache disabled, dual E5540 @2.53GHz,
    32bit kernel, FIB_TRIE, SLUB/NUMA)
    
    Before:
    
    real    0m51.179s
    user    0m15.329s
    sys     10m15.942s
    
    After:
    
    real	0m45.570s
    user	0m15.525s
    sys	9m56.669s
    
    With a small reordering of struct neighbour fields, subject of a
    following patch, (to separate refcnt from other read mostly fields)
    
    real	0m41.841s
    user	0m15.261s
    sys	8m45.949s
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    fc66f95c
dst.c 8.04 KB