On Thu, Jan 31, 2019 at 10:38:01AM +0100, Martynas Pumputis wrote:

Previously, memory allocated for a map was not accounted. Therefore,
this memory could not be taken into consideration by the cgroups
memory controller.

This patch introduces the "BPF_F_ACCOUNT_MEM" flag which enables
the memory accounting for a map, and it can be set during
the map creation ("BPF_MAP_CREATE") in "map_flags".

When enabled, we account only that amount of memory which is charged
against the "RLIMIT_MEMLOCK" limit.

To validate the change, first we create the memory cgroup-v1 "test-map":

    # mkdir /sys/fs/cgroup/memory/test-map

And then we run the following program against the cgroup:

    $ cat test_map.c
    <..>
    int main() {
        usleep(3 * 1000000);
        assert(bpf_create_map(BPF_MAP_TYPE_HASH, 8, 16, 65536, 0) > 0);
        usleep(3 * 1000000);
    }
    # cgexec -g memory:test-map ./test_map &
    # cat /sys/fs/cgroup/memory/test-map/memory{,.kmem}.usage_in_bytes
    397312
    258048

    <after 3 sec the map has been created>

    # bpftool map list
    19: hash  flags 0x0
        key 8B  value 16B  max_entries 65536  memlock 5771264B
    # cat /sys/fs/cgroup/memory/test-map/memory{,.kmem}.usage_in_bytes
    401408
    262144

As we can see, the memory allocated for map is not accounted, as
397312B + 5771264B > 401408B.

Next, we enabled the accounting and re-run the test:

    $ cat test_map.c
    <..>
    int main() {
        usleep(3 * 1000000);
        assert(bpf_create_map(BPF_MAP_TYPE_HASH, 8, 16, 65536, BPF_F_ACCOUNT_MEM) > 0);
        usleep(3 * 1000000);
    }
    # cgexec -g memory:test-map ./test_map &
    # cat /sys/fs/cgroup/memory/test-map/memory{,.kmem}.usage_in_bytes
    450560
    307200

    <after 3 sec the map has been created>

    # bpftool map list
    20: hash  flags 0x80
        key 8B  value 16B  max_entries 65536  memlock 5771264B
    # cat /sys/fs/cgroup/memory/test-map/memory{,.kmem}.usage_in_bytes
    6221824
    6078464

This time, the memory (including kmem) is accounted, as
450560B + 5771264B <= 6221824B

Acked-by: Yonghong Song <redacted>
Signed-off-by: Martynas Pumputis <redacted>

see my reply in other thread.