netdev - Re: [PATCH bpf-next 3/3] xdp: Add devmap_hash map type for looking up devices by hashed index

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Date:   Sat, 06 Jul 2019 10:41:41 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Y Song <ys114321@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Björn Töpel <bjorn.topel@...il.com>
Subject: Re: [PATCH bpf-next 3/3] xdp: Add devmap_hash map type for looking up devices by hashed index

Y Song <ys114321@...il.com> writes:

> On Fri, Jul 5, 2019 at 11:14 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>>
>> From: Toke Høiland-Jørgensen <toke@...hat.com>
>>
>> A common pattern when using xdp_redirect_map() is to create a device map
>> where the lookup key is simply ifindex. Because device maps are arrays,
>> this leaves holes in the map, and the map has to be sized to fit the
>> largest ifindex, regardless of how many devices actually are actually
>> needed in the map.
>>
>> This patch adds a second type of device map where the key is looked up
>> using a hashmap, instead of being used as an array index. This allows maps
>> to be densely packed, so they can be smaller.
>>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
>> ---
>>  include/linux/bpf.h                     |    7 +
>>  include/linux/bpf_types.h               |    1
>>  include/trace/events/xdp.h              |    3
>>  include/uapi/linux/bpf.h                |    7 +
>>  kernel/bpf/devmap.c                     |  192 +++++++++++++++++++++++++++++++
>>  kernel/bpf/verifier.c                   |    2
>>  net/core/filter.c                       |    9 +
>>  tools/bpf/bpftool/map.c                 |    1
>>  tools/include/uapi/linux/bpf.h          |    7 +
>>  tools/lib/bpf/libbpf_probes.c           |    1
>>  tools/testing/selftests/bpf/test_maps.c |   16 +++
>>  11 files changed, 237 insertions(+), 9 deletions(-)
>
> Could you break this patch into multiple commits for easy backporting
> and easy syncing to libbpf repo?
> For example, you can break it into 4 patches:
>    . kernel patch
>    . sync uapi bpf.h
>    . tools/lib/bpf/libbpf_probes.c
>    . other tools changes.

Sure, I'll send a v2.

-Toke