On Fri, Dec 17, 2021 at 9:13 AM Song Liu <songliubraving@xxxxxx> wrote: > > > > > 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. If BPF iterator approach works, that would be great! > > 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 > >>> >
