> On Dec 17, 2021, at 8:43 AM, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > On Fri, Dec 17, 2021 at 8:42 AM Andrii Nakryiko > <andrii.nakryiko@xxxxxxxxx> wrote: >> >> On Thu, Dec 16, 2021 at 5:53 PM Song Liu <songliubraving@xxxxxx> wrote: >>> >>> >>> >>>> On Dec 16, 2021, at 12:06 PM, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: >>>> >>>> On Tue, Dec 14, 2021 at 10:01 PM Song Liu <song@xxxxxxxxxx> 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? >>> >>> We can enable some debug option that dumps the page table. Then from the >>> page table, we can confirm the programs are running on a huge page. This >>> only works on x86_64 though. WDYT? >>> >> >> I don't know what exactly is involved, so it's hard to say. Ideally >> whatever we do doesn't complicate our CI setup. Can we use BPF tracing >> magic to check this from inside the kernel somehow? >> > > But I don't feel strongly about this, if it's hard to detect, it's > fine to not have a specific test (especially that it's very > architecture-specific) It will be more or less architecture-specific, as we need somehow walk the page table (with debug option or with BPF iterator). I will try something. Thanks, Song > >>> Thanks, >>> Song >>> >>> >>>> >>>> [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 >>>
