tree bacdf1b8025256fc591b1fd935a99f0b6af7466f
parent ba905f5e2f63d86ed4cfbd3d9096fb28d156f1ee
parent 3059303f59cf90a84e7fdef154ff0b215bcfaa97
author David S. Miller <davem@davemloft.net> 1454747686 -0500
committer David S. Miller <davem@davemloft.net> 1454747686 -0500

Merge branch 'bpf-per-cpu-maps'

Alexei Starovoitov says:

====================
bpf: introduce per-cpu maps

We've started to use bpf to trace every packet and atomic add
instruction (event JITed) started to show up in perf profile.
The solution is to do per-cpu counters.
For PERCPU_(HASH|ARRAY) map the existing bpf_map_lookup() helper
returns per-cpu area which bpf programs can use to store and
increment the counters. The BPF_MAP_LOOKUP_ELEM syscall command
returns areas from all cpus and user process aggregates the counters.
The usage example is in patch 6. The api turned out to be very
easy to use from bpf program and from user space.
Long term we were discussing to add 'bounded loop' instruction,
so bpf programs can do aggregation within the program which may
help some use cases. Right now user space aggregation of
per-cpu counters fits the best.

This patch set is new approach for per-cpu hash and array maps.
I've reused the map tests written by Martin and Ming, but
implementation and api is new. Old discussion here:
http://thread.gmane.org/gmane.linux.kernel/2123800/focus=2126435
====================

Signed-off-by: David S. Miller <davem@davemloft.net>