rte_pktmbuf_alloc() out of rte_mbufs

[Stephen Hemminger]

On Tue, 26 Nov 2024 23:50:25 +0000 (UTC)
amit sehas <cun23 at yahoo.com> wrote:

> Dumping the stats every 10 minutes suggest that there is no slow leak of buffers. The problem arises when the system is under stress and starts performing extra disk i/o. In this situation dpdk accumulates the buffers and does not return them back to the mempool right away thereby accumulating all the 4k buffers allocated to the queue.
> 
> rte_eth_tx_buffer_flush() should be flushing the buffers and returning them to the mempool ... is there any additional API that can make sure that this happens.

If you read the code in rte_ethdev.h
The rte_eth_tx_buffer_flush is just does a send of the packets that application has aggregated
via rte_eth_tx_buffer.

It does nothing vis-a-vis mempools are causing the driver (PMD) to complete transmits.
There are some tuneables such as tx_free_thresh which control when driver should
start freeing sent mbufs. 

Have you isolated the CPU's used by DPDK threads?
Is the application stalling because it starts swapping. You may have to mlockall to keep the
pages of application from swapping out.