Re: [PATCH v4 bpf-next 0/9] add bpf batch ops to process more than 1 elem

Yonghong Song
2020-01-14T23:12:46Z

On 1/14/20 8:46 AM, Brian Vazquez wrote:
> This patch series introduce batch ops that can be added to bpf maps to
> lookup/lookup_and_delete/update/delete more than 1 element at the time,
> this is specially useful when syscall overhead is a problem and in case
> of hmap it will provide a reliable way of traversing them.
>
> The implementation inclues a generic approach that could potentially be
> used by any bpf map and adds it to arraymap, it also includes the specific
> implementation of hashmaps which are traversed using buckets instead
> of keys.
>
> The bpf syscall subcommands introduced are:
>
> BPF_MAP_LOOKUP_BATCH
> BPF_MAP_LOOKUP_AND_DELETE_BATCH
> BPF_MAP_UPDATE_BATCH
> BPF_MAP_DELETE_BATCH
>
> The UAPI attribute is:
>
> struct { /* struct used by BPF_MAP_*_BATCH commands */
> __aligned_u64 in_batch; /* start batch,
> * NULL to start from beginning
> */
> __aligned_u64 out_batch; /* output: next start batch */
> __aligned_u64 keys;
> __aligned_u64 values;
> __u32 count; /* input/output:
> * input: # of key/value
> * elements
> * output: # of filled elements
> */
> __u32 map_fd;
> __u64 elem_flags;
> __u64 flags;
> } batch;
>
>
> in_batch and out_batch are only used for lookup and lookup_and_delete since
> those are the only two operations that attempt to traverse the map.
>
> update/delete batch ops should provide the keys/values that user wants
> to modify.
>
> Here are the previous discussions on the batch processing:
> - https://lore.kernel.org/bpf/20190724165803.87470-1-brianvv@google.com/
> - https://lore.kernel.org/bpf/20190829064502.2750303-1-yhs@fb.com/
> - https://lore.kernel.org/bpf/20190906225434.3635421-1-yhs@fb.com/
>
> Changelog sinve v3:
> - Do not use copy_to_user inside atomic region (Yonghong Song)
> - Use _opts approach on libbpf APIs (Andrii Nakryiko)
> - Drop generic_map_lookup_and_delete_batch support
> - Free malloc-ed memory in tests (Yonghong Song)
> - Reverse christmas tree (Yonghong Song)
> - Add acked labels

Thanks for the new revision! Overall looks good. Only have a few minor
comments. Also tested in my environment and everything works as expected.