• Eric Dumazet's avatar
    [NET]: Size listen hash tables using backlog hint · 72a3effa
    Eric Dumazet authored
    We currently allocate a fixed size (TCP_SYNQ_HSIZE=512) slots hash table for
    each LISTEN socket, regardless of various parameters (listen backlog for
    On x86_64, this means order-1 allocations (might fail), even for 'small'
    sockets, expecting few connections. On the contrary, a huge server wanting a
    backlog of 50000 is slowed down a bit because of this fixed limit.
    This patch makes the sizing of listen hash table a dynamic parameter,
    depending of :
    - net.core.somaxconn tunable (default is 128)
    - net.ipv4.tcp_max_syn_backlog tunable (default : 256, 1024 or 128)
    - backlog value given by user application  (2nd parameter of listen())
    For large allocations (bigger than PAGE_SIZE), we use vmalloc() instead of
    We still limit memory allocation with the two existing tunables (somaxconn &
    tcp_max_syn_backlog). So for standard setups, this patch actually reduce RAM
    Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
tcp_ipv4.c 47 KB