• Alexei Starovoitov's avatar
    bpf: add array type of eBPF maps · 28fbcfa0
    Alexei Starovoitov authored
    add new map type BPF_MAP_TYPE_ARRAY and its implementation
    
    - optimized for fastest possible lookup()
      . in the future verifier/JIT may recognize lookup() with constant key
        and optimize it into constant pointer. Can optimize non-constant
        key into direct pointer arithmetic as well, since pointers and
        value_size are constant for the life of the eBPF program.
        In other words array_map_lookup_elem() may be 'inlined' by verifier/JIT
        while preserving concurrent access to this map from user space
    
    - two main use cases for array type:
      . 'global' eBPF variables: array of 1 element with key=0 and value is a
        collection of 'global' variables which programs can use to keep the state
        between events
      . aggregation of tracing events into fixed set of buckets
    
    - all array elements pre-allocated and zero initialized at init time
    
    - key as an index in array and can only be 4 byte
    
    - map_delete_elem() returns EINVAL, since elements cannot be deleted
    
    - map_update_elem() replaces elements in an non-atomic way
      (for atomic updates hashtable type should be used instead)
    Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    28fbcfa0
Makefile 156 Bytes