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author | Alexei Starovoitov <ast@fb.com> | 2016-02-01 22:39:55 -0800 |
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committer | David S. Miller <davem@davemloft.net> | 2016-02-06 03:34:36 -0500 |
commit | 15a07b33814d14ca817887dbea8530728dc0fbe4 (patch) | |
tree | cf33026c34f2fbbe72e6ba3dd8079e3b0afa00ad /drivers/target | |
parent | a10423b87a7eae75da79ce80a8d9475047a674ee (diff) | |
download | linux-15a07b33814d14ca817887dbea8530728dc0fbe4.tar.bz2 |
bpf: add lookup/update support for per-cpu hash and array maps
The functions bpf_map_lookup_elem(map, key, value) and
bpf_map_update_elem(map, key, value, flags) need to get/set
values from all-cpus for per-cpu hash and array maps,
so that user space can aggregate/update them as necessary.
Example of single counter aggregation in user space:
unsigned int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
long values[nr_cpus];
long value = 0;
bpf_lookup_elem(fd, key, values);
for (i = 0; i < nr_cpus; i++)
value += values[i];
The user space must provide round_up(value_size, 8) * nr_cpus
array to get/set values, since kernel will use 'long' copy
of per-cpu values to try to copy good counters atomically.
It's a best-effort, since bpf programs and user space are racing
to access the same memory.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/target')
0 files changed, 0 insertions, 0 deletions