libbpf 1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it #369

anakryiko · 2021-08-18T23:45:13Z

Almost every single BPF application out there has to implement bumping RLIMIT_MEMLOCK. What's worse, starting from some recent kernel version, RLIMIT_MEMLOCK is not necessary anymore for loading BPF programs and maps. Instead of asking all users to implement this detection logic and RLIMIT_MEMLOCK adjustment, do a sensible thing automatically:

on older kernels, bump RLIMIT_MEMLOCK to infinity;
on newer kernels, do nothing.

Unfortunately, this is breaking change, so use libbpf_set_strict_mode() to allow this functionality. As of libbpf 1.0 it will be default behavior.

The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf/libbpf#369 Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf/libbpf#369 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>

The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf/libbpf#369 Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf/libbpf#369 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211214195904.1785155-2-andrii@kernel.org

The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf#369 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211214195904.1785155-2-andrii@kernel.org

[ upstream commit 216eaa7 ] The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf#369 [ Backport notes: Multiple conflicts, on all files, including (but not limited to): - bpf_sys() -> bpf_sys_fd() (I used the former) - bpf_create_map_xattr() -> bpf_map_create() (I bumped the rlimit in the former instead) - Missing features in enum kern_feature_id (I skipped them altogether) - Missing entries in libbpf.map (I skipped them too) ] Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211214195904.1785155-2-andrii@kernel.org Signed-off-by: Quentin Monnet <quentin@isovalent.com>

Bugzilla: https://bugzilla.redhat.com/2069046 Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git commit e542f2c4cd16d49392abf3349341d58153d3c603 Author: Andrii Nakryiko <andrii@kernel.org> Date: Tue Dec 14 11:59:03 2021 -0800 libbpf: Auto-bump RLIMIT_MEMLOCK if kernel needs it for BPF The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is one of the first extremely frustrating gotchas that all new BPF users go through and in some cases have to learn it a very hard way. Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem dropped the dependency on memlock and uses memcg-based memory accounting instead. Unfortunately, detecting memcg-based BPF memory accounting is far from trivial (as can be evidenced by this patch), so in practice most BPF applications still do unconditional RLIMIT_MEMLOCK increase. As we move towards libbpf 1.0, it would be good to allow users to forget about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment automatically. This patch paves the way forward in this matter. Libbpf will do feature detection of memcg-based accounting, and if detected, will do nothing. But if the kernel is too old, just like BCC, libbpf will automatically increase RLIMIT_MEMLOCK on behalf of user application ([0]). As this is technically a breaking change, during the transition period applications have to opt into libbpf 1.0 mode by setting LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling libbpf_set_strict_mode(). Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be called before the first bpf_prog_load(), bpf_btf_load(), or bpf_object__load() call, otherwise it has no effect and will return -EBUSY. [0] Closes: libbpf/libbpf#369 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211214195904.1785155-2-andrii@kernel.org Signed-off-by: Artem Savkov <asavkov@redhat.com>

anakryiko added this to the libbpf-1.0 milestone Aug 18, 2021

anakryiko added feature New feature or request good first issue Good for newcomers labels Aug 18, 2021

anakryiko changed the title ~~libbpf-1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it~~ libbpf 1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it Aug 18, 2021

anakryiko self-assigned this Oct 22, 2021

anakryiko added libbpf-1.0 Tasks related to libbpf-1.0 release and removed good first issue Good for newcomers labels Nov 30, 2021

mimullin-bbry mentioned this issue Dec 9, 2021

Bump-mem-limit is annoying. libbpf/libbpf-rs#159

Closed

anakryiko closed this as completed in 216eaa7 Dec 15, 2021

ed-flanagan mentioned this issue Jul 6, 2022

F36 Getting libbpf errors coreos/fedora-coreos-tracker#1164

Closed

geyslan mentioned this issue Sep 22, 2022

How do I remove memory limits？ aquasecurity/libbpfgo#247

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libbpf 1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it #369

libbpf 1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it #369

anakryiko commented Aug 18, 2021

libbpf 1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it #369

libbpf 1.0: bump RLIMIT_MEMLOCK automatically if kernel still needs it #369

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anakryiko commented Aug 18, 2021