netdev - Re: [PATCH v2 bpf-next] bpf: add optional memory accounting for maps

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Message-ID: <20190131183604.2e5ve5544glhjjre@ast-mbp.dhcp.thefacebook.com>
Date:   Thu, 31 Jan 2019 10:36:06 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Martynas Pumputis <m@...bda.lt>
Cc:     netdev@...r.kernel.org, ys114321@...il.com, ast@...nel.org,
        daniel@...earbox.net, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v2 bpf-next] bpf: add optional memory accounting for maps

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 <yhs@...com>
> Signed-off-by: Martynas Pumputis <m@...bda.lt>

see my reply in other thread.