[v3,bpf-next,0/8] bpf_prog_pack followup

Message

Song Liu May 20, 2022, 3:15 a.m. UTC

Changes v2 => v3:
1. Fix issues reported by kernel test robot <[e-mail]>.

Changes v1 => v2:
1. Add WARN to set_vm_flush_reset_perms() on huge pages. (Rick Edgecombe)
2. Simplify select_bpf_prog_pack_size. (Rick Edgecombe)

As of 5.18-rc6, x86_64 uses bpf_prog_pack on 4kB pages. This set contains
a few followups:
  1/8 - 3/8 fills unused part of bpf_prog_pack with illegal instructions.
  4/8 - 5/8 enables bpf_prog_pack on 2MB pages.

The primary goal of bpf_prog_pack is to reduce iTLB miss rate and reduce
direct memory mapping fragmentation. This leads to non-trivial performance
improvements.

For our web service production benchmark, bpf_prog_pack on 4kB pages
gives 0.5% to 0.7% more throughput than not using bpf_prog_pack.
bpf_prog_pack on 2MB pages 0.6% to 0.9% more throughput than not using
bpf_prog_pack. Note that 0.5% is a huge improvement for our fleet. I
believe this is also significant for other companies with many thousand
servers.

bpf_prog_pack on 2MB pages may use slightly more memory for systems
without many BPF programs. However, such waste in memory (<2MB) is within
noisy for modern x86_64 systems.

Song Liu (8):
  bpf: fill new bpf_prog_pack with illegal instructions
  x86/alternative: introduce text_poke_set
  bpf: introduce bpf_arch_text_invalidate for bpf_prog_pack
  module: introduce module_alloc_huge
  bpf: use module_alloc_huge for bpf_prog_pack
  vmalloc: WARN for set_vm_flush_reset_perms() on huge pages
  vmalloc: introduce huge_vmalloc_supported
  bpf: simplify select_bpf_prog_pack_size

 arch/x86/include/asm/text-patching.h |  1 +
 arch/x86/kernel/alternative.c        | 67 +++++++++++++++++++++++-----
 arch/x86/kernel/module.c             | 21 +++++++++
 arch/x86/net/bpf_jit_comp.c          |  5 +++
 include/linux/bpf.h                  |  1 +
 include/linux/moduleloader.h         |  5 +++
 include/linux/vmalloc.h              |  7 +++
 kernel/bpf/core.c                    | 43 ++++++++++--------
 kernel/module.c                      |  8 ++++
 mm/vmalloc.c                         |  5 +++
 10 files changed, 134 insertions(+), 29 deletions(-)

--
2.30.2