Re: [PATCH v4 0/5] powerpc/bpf: use BPF prog pack allocator

[Hari Bathini <hbathini@linux.ibm.com>]

Ping!

Comments, please..

On 08/09/23 6:57 pm, Hari Bathini wrote:
> Most BPF programs are small, but they consume a page each. For systems
> with busy traffic and many BPF programs, this may also add significant
> pressure on instruction TLB. High iTLB pressure usually slows down the
> whole system causing visible performance degradation for production
> workloads.
> 
> bpf_prog_pack, a customized allocator that packs multiple bpf programs
> into preallocated memory chunks, was proposed [1] to address it. This
> series extends this support on powerpc.
> 
> Patches 1 & 2 add the arch specific functions needed to support this
> feature. Patch 3 enables the support for powerpc and ensures cleanup
> is handled gracefully. Patch 4 introduces patch_instructions() that
> optimizes some calls while patching more than one instruction. Patch 5
> leverages this new function to improve time taken for JIT'ing BPF
> programs.
> 
> Note that the first 3 patches are sufficient to enable the support
> for bpf_prog_pack on powerpc. Patches 4 & 5 are to improve the JIT
> compilation time of BPF programs on powerpc.
> 
> Changes in v4:
> * Updated bpf_patch_instructions() definition in patch 1/5 so that
>    it doesn't have to be updated again in patch 2/5.
> * Addressed Christophe's comment on bpf_arch_text_invalidate() return
>    value in patch 2/5.
> 
> Changes in v3:
> * Fixed segfault issue observed on ppc32 due to inaccurate offset
>    calculation for branching.
> * Tried to minimize the performance impact for patch_instruction()
>    with the introduction of patch_instructions().
> * Corrected uses of u32* vs ppc_instr_t.
> * Moved the change that introduces patch_instructions() to after
>    enabling bpf_prog_pack support.
> * Added few comments to improve code readability.
> 
> [1] https://lore.kernel.org/bpf/20220204185742.271030-1-song@kernel.org/
> [2] https://lore.kernel.org/all/20230309180028.180200-1-hbathini@linux.ibm.com/
> 
> 
> Hari Bathini (5):
>    powerpc/bpf: implement bpf_arch_text_copy
>    powerpc/bpf: implement bpf_arch_text_invalidate for bpf_prog_pack
>    powerpc/bpf: use bpf_jit_binary_pack_[alloc|finalize|free]
>    powerpc/code-patching: introduce patch_instructions()
>    powerpc/bpf: use patch_instructions()
> 
>   arch/powerpc/include/asm/code-patching.h |   1 +
>   arch/powerpc/lib/code-patching.c         |  94 ++++++++++++---
>   arch/powerpc/net/bpf_jit.h               |  12 +-
>   arch/powerpc/net/bpf_jit_comp.c          | 144 ++++++++++++++++++-----
>   arch/powerpc/net/bpf_jit_comp32.c        |  13 +-
>   arch/powerpc/net/bpf_jit_comp64.c        |  10 +-
>   6 files changed, 211 insertions(+), 63 deletions(-)
>