[PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Jay Wang <hidden> · 2026-10-01
[PATCH bpf-next v4 01/12] bpf: pass the vmlinux BTF to btf_parse_module() and let it adopt the data · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 01/12] bpf: pass the vmlinux BTF to btf_parse_module() and let it adopt the data · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 02/12] bpf: split the kfunc, dtor kfunc and struct_ops registration bodies · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 02/12] bpf: split the kfunc, dtor kfunc and struct_ops registration bodies · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 03/12] bpf: fetch the vmlinux BTF where kernel types enter a program · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 03/12] bpf: fetch the vmlinux BTF where kernel types enter a program · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 04/12] bpf: take the vmlinux BTF from the btf_vmlinux module · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 04/12] bpf: take the vmlinux BTF from the btf_vmlinux module · bot+bpf-ci@kernel.org · 2026-10-01
Re: [PATCH bpf-next v4 04/12] bpf: take the vmlinux BTF from the btf_vmlinux module · sashiko-bot@kernel.org · 2026-10-02
Re: [PATCH bpf-next v4 04/12] bpf: take the vmlinux BTF from the btf_vmlinux module · Alexei Starovoitov <hidden> · 2026-10-02
[PATCH bpf-next v4 05/12] bpf, tracing: load the vmlinux BTF where tracefs and bpffs requests start · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 05/12] bpf, tracing: load the vmlinux BTF where tracefs and bpffs requests start · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 06/12] bpf: defer vmlinux kfunc and struct_ops registrations · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 06/12] bpf: defer vmlinux kfunc and struct_ops registrations · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 07/12] bpf: keep module BTF until the vmlinux BTF is available · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 07/12] bpf: keep module BTF until the vmlinux BTF is available · bot+bpf-ci@kernel.org · 2026-10-01
Re: [PATCH bpf-next v4 07/12] bpf: keep module BTF until the vmlinux BTF is available · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 08/12] bpf: expose deferred .BTF.base module BTF in sysfs from module load · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 08/12] bpf: expose deferred .BTF.base module BTF in sysfs from module load · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 09/12] bpf, trace, net: prepare CONFIG_DEBUG_INFO_BTF checks for a tristate · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 09/12] bpf, trace, net: prepare CONFIG_DEBUG_INFO_BTF checks for a tristate · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 10/12] resolve_btfids: add --btf_link to fill in .BTF.link records · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 10/12] resolve_btfids: add --btf_link to fill in .BTF.link records · bot+bpf-ci@kernel.org · 2026-10-01
Re: [PATCH bpf-next v4 10/12] resolve_btfids: add --btf_link to fill in .BTF.link records · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 11/12] tools, samples: take the vmlinux BTF from vmlinux.unstripped first · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 11/12] tools, samples: take the vmlinux BTF from vmlinux.unstripped first · sashiko-bot@kernel.org · 2026-10-02
[PATCH bpf-next v4 12/12] kbuild, bpf: allow building the vmlinux BTF as a module · Jay Wang <hidden> · 2026-10-01
Re: [PATCH bpf-next v4 12/12] kbuild, bpf: allow building the vmlinux BTF as a module · sashiko-bot@kernel.org · 2026-10-02
Re: [PATCH bpf-next v4 12/12] kbuild, bpf: allow building the vmlinux BTF as a module · Alan Maguire <hidden> · 2026-10-02
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Ihor Solodrai <ihor.solodrai@linux.dev> · 2026-10-02
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Jay Wang <hidden> · 2026-10-02
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Alan Maguire <hidden> · 2026-10-02
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Ihor Solodrai <ihor.solodrai@linux.dev> · 2026-10-02
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Alexei Starovoitov <hidden> · 2026-10-03
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Alan Maguire <hidden> · 2026-10-03
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Alexei Starovoitov <hidden> · 2026-10-03
Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory · Jay Wang <hidden> · 2026-10-04

Re: [PATCH bpf-next v4 00/12] bpf: make the vmlinux BTF an on-demand loadable module (CONFIG_DEBUG_INFO_BTF=m) to save ~5.4 MB memory

From: Jay Wang <hidden>
Date: 2026-10-02 07:34:23
Also in: bpf, linux-doc, linux-kbuild, linux-kselftest, linux-modules, linux-perf-users, linux-trace-kernel, lkml, rust-for-linux, sched-ext

A question I had: is it really worth 2k of complicated kernel code to
*maybe sometimes* save <10Mb of memory?

There are many reasons this is worth it.  The main ones:

1. This did not start from a number we picked, but from a real use
   case: users who run large fleets of small instances, 1 GiB of
   memory or less, with their workloads sized to fit.  We are not able
   to disclose more detail, but for them 5.4 MB on every instance is
   real money, and it can be exactly what pushes a workload over its
   memory budget and onto the next instance size.  That is why we took
   this on, even though we knew it would not be a small change.

2. Loading code and data only when a system needs them is what kernel
   modules exist for.  And most of them take well under ~1 MB once
   loaded (nf_conntrack, overlay, vfat); even big ones like ext4, kvm
   and btrfs stay around 1-2.5 MB.  The vmlinux BTF is 5.4 MB.

3. We are not alone in trying to keep BTF out of memory until it is
   needed.  The inline BTF work [1] plans to deliver its data, which
   is even larger, through a module too.  The .BTF.link record and the
   resolve_btfids option that serve both are already part of this
   series (patch 10), so this is not machinery for the vmlinux BTF
   alone.

Do those tiny VMs that you target run systemd with BPF LSM?

Not necessarily, and that is the image's choice.  Even with BPF LSM
built in and bpf in CONFIG_LSM, memory-conscious users can turn it off
at boot with an lsm= list that leaves it out, and then systemd does not
load restrict_fs at all.

And even where user space is in the way, which as above it does not
have to be, the answer is to fix user space so it gets this win too,
not to give up on it.

If the answer is "yes" for the majority of them,

"The majority" is also hard to pin down here: what runs at boot
depends on the user space packages built into each image, and on the
workload.

So the question should be what it takes to make this work, not whether
to drop it because it is complicated.  If there are ways to cut it
down, or issues found in the implementation, we would be happy to take
them and go through every one.


[1] https://lore.kernel.org/bpf/20260916074118.1007116-1-alan.maguire@oracle.com/ (local)

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