On Thu, Oct 28, 2021 at 5:15 PM Joanne Koong <joannekoong@xxxxxx> wrote: > > On 10/28/21 11:15 AM, Andrii Nakryiko wrote: > > > On Wed, Oct 27, 2021 at 4:45 PM Joanne Koong <joannekoong@xxxxxx> wrote: > >> This patch adds the kernel-side changes for the implementation of > >> a bpf bloom filter map. > >> > >> The bloom filter map supports peek (determining whether an element > >> is present in the map) and push (adding an element to the map) > >> operations.These operations are exposed to userspace applications > >> through the already existing syscalls in the following way: > >> > >> BPF_MAP_LOOKUP_ELEM -> peek > >> BPF_MAP_UPDATE_ELEM -> push > >> > >> The bloom filter map does not have keys, only values. In light of > >> this, the bloom filter map's API matches that of queue stack maps: > >> user applications use BPF_MAP_LOOKUP_ELEM/BPF_MAP_UPDATE_ELEM > >> which correspond internally to bpf_map_peek_elem/bpf_map_push_elem, > >> and bpf programs must use the bpf_map_peek_elem and bpf_map_push_elem > >> APIs to query or add an element to the bloom filter map. When the > >> bloom filter map is created, it must be created with a key_size of 0. > >> > >> For updates, the user will pass in the element to add to the map > >> as the value, with a NULL key. For lookups, the user will pass in the > >> element to query in the map as the value, with a NULL key. In the > >> verifier layer, this requires us to modify the argument type of > >> a bloom filter's BPF_FUNC_map_peek_elem call to ARG_PTR_TO_MAP_VALUE; > >> as well, in the syscall layer, we need to copy over the user value > >> so that in bpf_map_peek_elem, we know which specific value to query. > >> > >> A few things to please take note of: > >> * If there are any concurrent lookups + updates, the user is > >> responsible for synchronizing this to ensure no false negative lookups > >> occur. > >> * The number of hashes to use for the bloom filter is configurable from > >> userspace. If no number is specified, the default used will be 5 hash > >> functions. The benchmarks later in this patchset can help compare the > >> performance of using different number of hashes on different entry > >> sizes. In general, using more hashes decreases both the false positive > >> rate and the speed of a lookup. > >> * Deleting an element in the bloom filter map is not supported. > >> * The bloom filter map may be used as an inner map. > >> * The "max_entries" size that is specified at map creation time is used > >> to approximate a reasonable bitmap size for the bloom filter, and is not > >> otherwise strictly enforced. If the user wishes to insert more entries > >> into the bloom filter than "max_entries", they may do so but they should > >> be aware that this may lead to a higher false positive rate. > >> > >> Signed-off-by: Joanne Koong <joannekoong@xxxxxx> > >> --- > > Don't forget to keep received Acks between revisions. > > > > Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > Can you elaborate a little on how to keep received Acks between revisions? > > Should I copy and paste the "Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>" Yes, it's all manual. See [0] for an example. [0] https://patchwork.kernel.org/project/netdevbpf/patch/20211028063501.2239335-9-memxor@xxxxxxxxx/ > line into the commit message for the patch? Or should this information be > in the subject line of the email for the patch? Or in the patchset series' > cover letter? Thanks! > > > > >> include/linux/bpf.h | 1 + > >> include/linux/bpf_types.h | 1 + > >> include/uapi/linux/bpf.h | 9 ++ > >> kernel/bpf/Makefile | 2 +- > >> kernel/bpf/bloom_filter.c | 195 +++++++++++++++++++++++++++++++++ > >> kernel/bpf/syscall.c | 24 +++- > >> kernel/bpf/verifier.c | 19 +++- > >> tools/include/uapi/linux/bpf.h | 9 ++ > >> 8 files changed, 253 insertions(+), 7 deletions(-) > >> create mode 100644 kernel/bpf/bloom_filter.c > > [...]
