linux-kernel - Re: [PATCH v2 bpf-next 0/7] bpf_prog

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Date:   Thu, 16 Dec 2021 12:06:05 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Song Liu <song@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Kernel Team <kernel-team@...com>,
        Peter Ziljstra <peterz@...radead.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH v2 bpf-next 0/7] bpf_prog_pack allocator

On Tue, Dec 14, 2021 at 10:01 PM Song Liu <song@...nel.org> wrote:
>
> Changes v1 => v2:
> 1. Use text_poke instead of writing through linear mapping. (Peter)
> 2. Avoid making changes to non-x86_64 code.
>
> Most BPF programs are small, but they consume a page each. For systems
> with busy traffic and many BPF programs, this could also add significant
> pressure to instruction TLB.
>
> This set tries to solve this problem with customized allocator that pack
> multiple programs into a huge page.
>
> Patches 1-5 prepare the work. Patch 6 contains key logic of the allocator.
> Patch 7 uses this allocator in x86_64 jit compiler.
>

There are test failures, please see [0]. But I was also wondering if
there could be an explicit selftest added to validate that all this
huge page machinery is actually activated and working as expected?

  [0] https://github.com/kernel-patches/bpf/runs/4530372387?check_suite_focus=true

> Song Liu (7):
>   x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP
>   bpf: use bytes instead of pages for bpf_jit_[charge|uncharge]_modmem
>   bpf: use size instead of pages in bpf_binary_header
>   bpf: add a pointer of bpf_binary_header to bpf_prog
>   x86/alternative: introduce text_poke_jit
>   bpf: introduce bpf_prog_pack allocator
>   bpf, x86_64: use bpf_prog_pack allocator
>
>  arch/x86/Kconfig                     |   1 +
>  arch/x86/include/asm/text-patching.h |   1 +
>  arch/x86/kernel/alternative.c        |  28 ++++
>  arch/x86/net/bpf_jit_comp.c          |  93 ++++++++++--
>  include/linux/bpf.h                  |   4 +-
>  include/linux/filter.h               |  23 ++-
>  kernel/bpf/core.c                    | 213 ++++++++++++++++++++++++---
>  kernel/bpf/trampoline.c              |   6 +-
>  8 files changed, 328 insertions(+), 41 deletions(-)
>
> --
> 2.30.2