Force driver to free sent buffers?

[Alan Beadle <ab.beadle@gmail.com>]

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
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?

Thanks,
-Alan