Repo for tips / tricks / common code?

Repo for tips / tricks / common code?

[Barret Rhoden]

Hi -

Is there any interest in a repo or something for reusable BPF code bits? 
  I've got some stuff that I do in my programs that might be useful to 
others, but not to the level of a full bpf helper.

For instance, one technique I've developed is to have list-like data 
structures for *mmappable* data that are e.g. per-cpu and per-task. 
Internally, it's an Array map, and each element is identified by its 
index in the array instead of by point.  And the linked-list is built 
with index integers instead of pointers.

Anyway, that's just an example, and I imagine other people have their 
own techniques.  I've got the code sitting in an open-source repo 
elsewhere, and had a couple people off-list ask me about it.  I could 
email it to the list, but it'd get lost in the noise.

If you're curious about specifics, the linked list code is here [1], and 
I briefly mentioned the data structures in my LPC 22 talk [2].  I've got 
an AVL tree that works with this stuff too.

Thanks,
Barret


[1] https://github.com/google/ghost-userspace/blob/main/lib/queue.bpf.h
[2] 
https://lpc.events/event/16/contributions/1365/attachments/986/1912/lpc22-ebpf-kernel-scheduling-with-ghost.pdf

Re: Repo for tips / tricks / common code?

[Alexei Starovoitov]

On Tue, Jul 18, 2023 at 9:15 AM Barret Rhoden <brho@google.com> wrote:
>
> Hi -
>
> Is there any interest in a repo or something for reusable BPF code bits?
>   I've got some stuff that I do in my programs that might be useful to
> others, but not to the level of a full bpf helper.
>
> For instance, one technique I've developed is to have list-like data
> structures for *mmappable* data that are e.g. per-cpu and per-task.
> Internally, it's an Array map, and each element is identified by its
> index in the array instead of by point.  And the linked-list is built
> with index integers instead of pointers.
>
> Anyway, that's just an example, and I imagine other people have their
> own techniques.  I've got the code sitting in an open-source repo
> elsewhere, and had a couple people off-list ask me about it.  I could
> email it to the list, but it'd get lost in the noise.
>
> If you're curious about specifics, the linked list code is here [1], and
> I briefly mentioned the data structures in my LPC 22 talk [2].  I've got
> an AVL tree that works with this stuff too.

I think github would be the best place for such code.
https://github.com/libbpf/.../ maybe?

> Thanks,
> Barret
>
>
> [1] https://github.com/google/ghost-userspace/blob/main/lib/queue.bpf.h

btw, I'm working on adding 32-bit pointers to BPF,
so such link lists, AVL or anything else will look more natural and
will be mmap-able to user space as well.
So bpf program can implement its own hash table or rbtree and
user space can walk/modify it in parallel without crashing the kernel,
but potentially 'segfaulting' bpf program.
Still need to figure out a sane locking mechanism.

> [2]
> https://lpc.events/event/16/contributions/1365/attachments/986/1912/lpc22-ebpf-kernel-scheduling-with-ghost.pdf
>

Re: Repo for tips / tricks / common code?

[Donald Hunter]

Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> On Tue, Jul 18, 2023 at 9:15 AM Barret Rhoden <brho@google.com> wrote:
>>
>> Hi -
>>
>> Is there any interest in a repo or something for reusable BPF code bits?
>>   I've got some stuff that I do in my programs that might be useful to
>> others, but not to the level of a full bpf helper.
>>
>> For instance, one technique I've developed is to have list-like data
>> structures for *mmappable* data that are e.g. per-cpu and per-task.
>> Internally, it's an Array map, and each element is identified by its
>> index in the array instead of by point.  And the linked-list is built
>> with index integers instead of pointers.
>>
>> Anyway, that's just an example, and I imagine other people have their
>> own techniques.  I've got the code sitting in an open-source repo
>> elsewhere, and had a couple people off-list ask me about it.  I could
>> email it to the list, but it'd get lost in the noise.
>>
>> If you're curious about specifics, the linked list code is here [1], and
>> I briefly mentioned the data structures in my LPC 22 talk [2].  I've got
>> an AVL tree that works with this stuff too.
>
> I think github would be the best place for such code.
> https://github.com/libbpf/.../ maybe?

Or potentially:

https://github.com/xdp-project/bpf-examples

>
>> Thanks,
>> Barret