From: Yonghong Song <yhs@fb.com>
To: KP Singh <kpsingh@kernel.org>
Cc: Song Liu <songliubraving@fb.com>, bpf <bpf@vger.kernel.org>,
Networking <netdev@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>, <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Kernel Team <kernel-team@fb.com>, Hao Luo <haoluo@google.com>,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs
Date: Mon, 11 Jan 2021 07:56:17 -0800 [thread overview]
Message-ID: <8b8e687d-b572-ab12-8595-3ab14d58caad@fb.com> (raw)
In-Reply-To: <CACYkzJ7eJa7C8=eRL3XoRjmccgD0udoyoi38MOjo7H0rsnZOYA@mail.gmail.com>
On 1/11/21 2:17 AM, KP Singh wrote:
> On Mon, Jan 11, 2021 at 7:27 AM Yonghong Song <yhs@fb.com> wrote:
>>
>>
>>
>> On 1/8/21 3:19 PM, Song Liu wrote:
>>> To access per-task data, BPF program typically creates a hash table with
>>> pid as the key. This is not ideal because:
>>> 1. The use need to estimate requires size of the hash table, with may be
>>> inaccurate;
>>> 2. Big hash tables are slow;
>>> 3. To clean up the data properly during task terminations, the user need
>>> to write code.
>>>
>>> Task local storage overcomes these issues and becomes a better option for
>>> these per-task data. Task local storage is only available to BPF_LSM. Now
>>> enable it for tracing programs.
>>>
>>> Reported-by: kernel test robot <lkp@intel.com>
>>> Signed-off-by: Song Liu <songliubraving@fb.com>
>>> ---
>
> [...]
>
>>> struct cfs_rq;
>>> struct fs_struct;
>>> @@ -1348,6 +1349,10 @@ struct task_struct {
>>> /* Used by LSM modules for access restriction: */
>>> void *security;
>>> #endif
>>> +#ifdef CONFIG_BPF_SYSCALL
>>> + /* Used by BPF task local storage */
>>> + struct bpf_local_storage *bpf_storage;
>>> +#endif
>>
>> I remembered there is a discussion where KP initially wanted to put
>> bpf_local_storage in task_struct, but later on changed to
>> use in lsm as his use case mostly for lsm. Did anybody
>> remember the details of the discussion? Just want to be
>> sure what is the concern people has with putting bpf_local_storage
>> in task_struct and whether the use case presented by
>> Song will justify it.
>>
>
> If I recall correctly, the discussion was about inode local storage and
> it was decided to use the security blob since the use-case was only LSM
> programs. Since we now plan to use it in tracing,
> detangling the dependency from CONFIG_BPF_LSM
> sounds logical to me.
Sounds good. Thanks for explanation.
>
>
>>>
>>> #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
>>> unsigned long lowest_stack;
>>> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
>>> index d1249340fd6ba..ca995fdfa45e7 100644
>>> --- a/kernel/bpf/Makefile
>>> +++ b/kernel/bpf/Makefile
>>> @@ -8,9 +8,8 @@ CFLAGS_core.o += $(call cc-disable-warning, override-init) $(cflags-nogcse-yy)
>>>
>>> obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o
>>> obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
>>> -obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
>>> +obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o bpf_task_storage.o
>>> obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o
>>> -obj-${CONFIG_BPF_LSM} += bpf_task_storage.o
>>> obj-$(CONFIG_BPF_SYSCALL) += disasm.o
>>> obj-$(CONFIG_BPF_JIT) += trampoline.o
>>> obj-$(CONFIG_BPF_SYSCALL) += btf.o
>> [...]
next prev parent reply other threads:[~2021-01-11 15:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210108231950.3844417-1-songliubraving@fb.com>
[not found] ` <20210108231950.3844417-2-songliubraving@fb.com>
2021-01-11 6:27 ` [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs Yonghong Song
2021-01-11 10:17 ` KP Singh
2021-01-11 15:56 ` Yonghong Song [this message]
2021-01-11 10:14 ` KP Singh
2021-01-11 23:16 ` Song Liu
2021-01-11 17:16 ` Yonghong Song
2021-01-11 18:56 ` Martin KaFai Lau
2021-01-11 21:35 ` KP Singh
2021-01-11 21:58 ` Martin KaFai Lau
2021-01-11 23:45 ` Song Liu
2021-01-12 16:32 ` Yonghong Song
2021-01-12 16:53 ` KP Singh
2021-01-15 23:34 ` Song Liu
2021-01-16 0:55 ` Yonghong Song
2021-01-16 1:12 ` Song Liu
2021-01-16 1:50 ` Yonghong Song
2021-01-11 23:41 ` Song Liu
2021-01-12 18:21 ` Martin KaFai Lau
[not found] ` <20210108231950.3844417-4-songliubraving@fb.com>
2021-01-11 17:37 ` [PATCH bpf-next 3/4] bpf: runqslower: prefer use local vmlinux Yonghong Song
[not found] ` <20210108231950.3844417-5-songliubraving@fb.com>
2021-01-11 17:49 ` [PATCH bpf-next 4/4] bpf: runqslower: use task local storage Yonghong Song
2021-01-11 22:54 ` Song Liu
2021-01-12 3:24 ` Yonghong Song
2021-01-12 7:14 ` Andrii Nakryiko
2021-01-12 7:33 ` Yonghong Song
[not found] ` <20210108231950.3844417-3-songliubraving@fb.com>
2021-01-11 17:30 ` [PATCH bpf-next 2/4] selftests/bpf: add non-BPF_LSM test for " Yonghong Song
2021-01-11 17:44 ` KP Singh
2021-01-11 22:50 ` Song Liu
2021-01-11 22:49 ` Song Liu
2021-01-12 7:06 ` Andrii Nakryiko
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