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authorAlexei Starovoitov <ast@fb.com>2016-02-01 22:39:53 -0800
committerDavid S. Miller <davem@davemloft.net>2016-02-06 03:34:35 -0500
commit824bd0ce6c7c43a9e1e210abf124958e54d88342 (patch)
tree10d1841e462152a97c3d855f17568684d5246dd0 /kernel/bpf/arraymap.c
parentba905f5e2f63d86ed4cfbd3d9096fb28d156f1ee (diff)
downloadlinux-sh-824bd0ce6c7c43a9e1e210abf124958e54d88342.tar.gz
bpf: introduce BPF_MAP_TYPE_PERCPU_HASH map
Introduce BPF_MAP_TYPE_PERCPU_HASH map type which is used to do accurate counters without need to use BPF_XADD instruction which turned out to be too costly for high-performance network monitoring. In the typical use case the 'key' is the flow tuple or other long living object that sees a lot of events per second. bpf_map_lookup_elem() returns per-cpu area. Example: struct { u32 packets; u32 bytes; } * ptr = bpf_map_lookup_elem(&map, &key); /* ptr points to this_cpu area of the value, so the following * increments will not collide with other cpus */ ptr->packets ++; ptr->bytes += skb->len; bpf_update_elem() atomically creates a new element where all per-cpu values are zero initialized and this_cpu value is populated with given 'value'. Note that non-per-cpu hash map always allocates new element and then deletes old after rcu grace period to maintain atomicity of update. Per-cpu hash map updates element values in-place. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf/arraymap.c')
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