On Thu, Apr 4, 2024 at 2:03 PM Puranjay Mohan <puranjay12@xxxxxxxxx> wrote: > > Hi Andrii, > > On Thu, Apr 4, 2024 at 6:12 PM Andrii Nakryiko > <andrii.nakryiko@xxxxxxxxx> wrote: > > > > On Mon, Apr 1, 2024 at 7:13 PM Andrii Nakryiko <andrii@xxxxxxxxxx> wrote: > > > > > > Add a new BPF instruction for resolving per-CPU memory addresses. > > > > > > New instruction is a special form of BPF_ALU64 | BPF_MOV | BPF_DW, with > > > insns->off set to BPF_ADDR_PERCPU (== -1). It resolves provided per-CPU offset > > > to an absolute address where per-CPU data resides for "this" CPU. > > > > > > This patch set implements support for it in x86-64 BPF JIT only. > > > > > > Using the new instruction, we also implement inlining for three cases: > > > - bpf_get_smp_processor_id(), which allows to avoid unnecessary trivial > > > function call, saving a bit of performance and also not polluting LBR > > > records with unnecessary function call/return records; > > > - PERCPU_ARRAY's bpf_map_lookup_elem() is completely inlined, bringing its > > > performance to implementing per-CPU data structures using global variables > > > in BPF (which is an awesome improvement, see benchmarks below); > > > - PERCPU_HASH's bpf_map_lookup_elem() is partially inlined, just like the > > > same for non-PERCPU HASH map; this still saves a bit of overhead. > > > > > > To validate performance benefits, I hacked together a tiny benchmark doing > > > only bpf_map_lookup_elem() and incrementing the value by 1 for PERCPU_ARRAY > > > (arr-inc benchmark below) and PERCPU_HASH (hash-inc benchmark below) maps. To > > > establish a baseline, I also implemented logic similar to PERCPU_ARRAY based > > > on global variable array using bpf_get_smp_processor_id() to index array for > > > current CPU (glob-arr-inc benchmark below). > > Can you share the code for these benchmarks? I want to use the same to > compare the performance > on ARM64. > Sure, see [0]. You can run: $ ./benchs/run_bench_trigger.sh glob-arr-inc arr-inc hash-inc from tools/testing/selftest/bpf directory to get something like $ ./benchs/run_bench_trigger.sh glob-arr-inc arr-inc hash-inc glob-arr-inc : 243.196 ± 7.879M/s arr-inc : 218.139 ± 4.407M/s hash-inc : 97.727 ± 3.643M/s [0] https://github.com/anakryiko/linux/commit/8dec900975ef1a0308a7862154735549d6b66f64 > Thanks, > Puranjay
