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) > > 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 > >
