Re: Force driver to free sent buffers?

[David Marchand <david.marchand@redhat.com>]

On Sun, Oct 6, 2024 at 6:39 PM Alan Beadle <ab.beadle@gmail.com> wrote:
>
> Hi everyone,
>
> Based on my thread from last week, I am using rte_mbuf_refcnt_update()
> to increment the mbuf refcnts so that the driver will not free buffers
> before my local readers are done with them.
> I am also maintaining a queue of mbufs that local readers are finished
> with, and periodically using rte_mbuf_refcnt_read() to see if the
> refcnt is 1 yet, so that they can be freed or reused.
>
> An aside: Is there any problem with reuse of mbufs? Without actually
> freeing and re-allocating it, that is? I plan to do this in order to
> avoid having to link new mbufs to other reused data structures in my
> application.
>
> The current problem is as follows: My application has a separate
> unrelated heap (special purpose and bounded in size) and this heap
> runs out of memory after a brief time because of having to track so
> many unfreed mbufs. It appears that none of the mbufs are being freed

Would it help to store this per-mbuf tracking context into a private area?

You can ask for a per-mbuf private area at the mempool creation, see priv_size.
https://doc.dpdk.org/api/rte__mbuf_8h.html#a593921f13307803b94bbb4e0932db962


> by the driver after being sent, and it looks like it won't free them
> until it runs out of descriptors, which is too long for my situation.
>
> I have confirmed that the packets are being sent (received on other PC
> with wireshark) and should be freeable. Is there a way to force the
> driver to free sent mbufs earlier than when it runs out of
> descriptors?


-- 
David Marchand