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authorAlexei Starovoitov <ast@plumgrid.com>2014-11-13 17:36:46 -0800
committerDavid S. Miller <davem@davemloft.net>2014-11-18 13:43:59 -0500
commit28fbcfa08d8ed7c5a50d41a0433aad222835e8e3 (patch)
tree1ef9417be1eb51e76456b3f2dbaf080c48883c32 /samples
parent0f8e4bd8a1fc8c4185f1630061d0a1f2d197a475 (diff)
downloadlinux-sh-28fbcfa08d8ed7c5a50d41a0433aad222835e8e3.tar.gz
bpf: add array type of eBPF maps
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: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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