Messages in this thread | | | Subject | Re: [PATCH bpf-next v4 3/3] bpf, arm64: use bpf_jit_binary_pack_alloc | From | Daniel Borkmann <> | Date | Wed, 16 Aug 2023 15:25:48 +0200 |
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On 8/15/23 4:09 PM, Puranjay Mohan wrote: > Hi Everyone, > > [+cc Björn] > > On Mon, Jun 26, 2023 at 10:58 AM Puranjay Mohan <puranjay12@gmail.com> wrote: >> >> Use bpf_jit_binary_pack_alloc for memory management of JIT binaries in >> ARM64 BPF JIT. The bpf_jit_binary_pack_alloc creates a pair of RW and RX >> buffers. The JIT writes the program into the RW buffer. When the JIT is >> done, the program is copied to the final RX buffer >> with bpf_jit_binary_pack_finalize. >> >> Implement bpf_arch_text_copy() and bpf_arch_text_invalidate() for ARM64 >> JIT as these functions are required by bpf_jit_binary_pack allocator. >> >> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com> >> Acked-by: Song Liu <song@kernel.org> > > [...] > >> +int bpf_arch_text_invalidate(void *dst, size_t len) >> +{ >> + __le32 *ptr; >> + int ret; >> + >> + for (ptr = dst; len >= sizeof(u32); len -= sizeof(u32)) { >> + ret = aarch64_insn_patch_text_nosync(ptr++, AARCH64_BREAK_FAULT); >> + if (ret) >> + return ret; >> + } >> + >> + return 0; >> +} >> + > > While testing the same patch for riscv bpf jit, Björn found that > ./test_tag is taking a lot of > time to complete. He found that bpf_arch_text_invalidate() is calling > patch_text_nosync() in RISCV > and aarch64_insn_patch_text_nosync() here in ARM64. Both of the > implementations call these functions > in a loop for each word. The problem is that every call to > patch_text_nosync()/aarch64_insn_patch_text_nosync() > would clean the cache. This will make this > function(bpf_arch_text_invalidate) really slow. > > I did some testing using the vmtest.sh script on ARM64 with and > without the patches, here are the results: > > With Prog Pack patches applied: > ========================= > > root@(none):/# time ./root/bpf/test_tag > test_tag: OK (40945 tests) > > real 3m2.001s > user 0m1.644s > sys 2m40.132s > > Without Prog Pack: > =============== > > root@(none):/# time ./root/bpf/test_tag > test_tag: OK (40945 tests) > > real 0m26.809s > user 0m1.591s > sys 0m24.106s > > As you can see the current implementation of > bpf_arch_text_invalidate() is really slow. I need to > implement a new function: aarch64_insn_set_text_nosync() and use it in > bpf_arch_text_invalidate() > rather than calling aarch64_insn_patch_text_nosync() in a loop.
Ok, thanks for looking into this. I'm going to toss the current version from patchwork in that case and will wait for a v5 from your side.
> In the longer run, it would be really helpful if we have a standard > text_poke API like x86 in every architecture.
Likely independent of this series, but in case you see potential to consolidate generic pieces, it might be worth a look after the arm64/riscv bits landed.
Thanks for working on this, Puranjay!
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