[PATCH 00/13] mm: jit/text allocator

Kent Overstreet kent.overstreet at linux.dev
Mon Jun 5 07:40:01 AEST 2023

On Sun, Jun 04, 2023 at 02:22:30PM -0700, Song Liu wrote:
> On Sun, Jun 4, 2023 at 11:02 AM Kent Overstreet
> <kent.overstreet at linux.dev> wrote:
> >
> > On Fri, Jun 02, 2023 at 11:20:58AM -0700, Song Liu wrote:
> > > IIUC, arm64 uses VMALLOC address space for BPF programs. The reason
> > > is each BPF program uses at least 64kB (one page) out of the 128MB
> > > address space. Puranjay Mohan (CC'ed) is working on enabling
> > > bpf_prog_pack for arm64. Once this work is done, multiple BPF programs
> > > will be able to share a page. Will this improvement remove the need to
> > > specify a different address range for BPF programs?
> >
> > Can we please stop working on BPF specific sub page allocation and focus
> > on doing this in mm/? This never should have been in BPF in the first
> > place.
> That work is mostly independent of the allocator work we are discussing here.
> The goal Puranjay's work is to enable the arm64 BPF JIT engine to use a
> ROX allocator. The allocator could be the bpf_prog_pack allocator, or jitalloc,
> or module_alloc_type. Puranjay is using bpf_prog_alloc for now. But once
> jitalloc or module_alloc_type (either one) is merged, we will migrate BPF
> JIT engines (x86_64 and arm64) to the new allocator and then tear down
> bpf_prog_pack.
> Does this make sense?

Yeah, as long as that's the plan. Maybe one of you could tell us what
issues were preventing prog_pack from being used in the first place, it
might be relevant - this is the time to get the new allocator API right.

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