On 09/10/2018 08:04 PM, Alexei Starovoitov wrote:
On Fri, Sep 7, 2018 at 1:40 PM, Mauricio Vasquez
<mauricio.vasq...@polito.it> wrote:
I read the Joe's proposal and using that for this problem looks like a nice
solution.
I think a good trade-off for now would be to go ahead with a queue/stack map
without preallocating support (or maybe include it having always in mind
that this issue has to be solved in the near future) and then, as a
separated work, try to use Joe's proposal in the map helpers.
What do you think?
the problem with such approach is that it would mean that
non-prealloc stack/queue api will be different from future one
after verifier will get smarter.
The alternative would be to support by-value api only.
Meaning let stack/queue support value_size = 1,2,4,8 byte only.
Then bpf_push|pop_elem() helper will be by-value
instead of returning a pointer.
No rcu callback issues and implementation on the kernel
side can be much simpler.
I think simple array of value_size elems with head/tail indices
will be enough.
Once we have Joe's verifier improvements
we can add alloc/free bpf object management facility
and use 8-byte stack/queue mapas a stack of pointers.
I think decoupling memory operations alloc/free from
stack push/pop would be additional benefit of such design.
I agree, this suffices our requirements and avoid RCU issues.
Will spin a V3 implementing it this week.
