[dpdk-users] IPv4 Fragmentation - indirect pool gets exhausted

[Vishal Mohan]

Hi,

I m trying to fragmentation an IPv4 packet using the below logic:

/////////////////////////////////////////////////////////////////////

~after pkts ingress~

struct rte_port_ring_writer *p = port_out->h_port;

pool_direct = rte_mempool_lookup("MEMPOOL0");
pool_indirect = rte_mempool_lookup("MEMPOOL1");

printf("before frag mempool size d %d in 
%d\n",rte_mempool_avail_count(pool_direct),rte_mempool_avail_count(pool_indirect));

struct rte_mbuf *frag_pkts[MAX_FRAG_SIZE];
int out_pkts =    rte_ipv4_fragment_packet (m, frag_pkts, n_frags, ip_mtu,
                                                                                
                                pool_direct, pool_indirect);

printf("after frag mempool size d %d in 
%d\n",rte_mempool_avail_count(pool_direct),rte_mempool_avail_count(pool_indirect));

if(out_pkts > 0)
port_out->ops.f_tx_bulk(port_out->h_port,frag_pkts,RTE_LEN2MASK(out_pkts, 
uint64_t));
else
printf("frag failed\n");

rte_pktmbuf_free<https://doc.dpdk.org/api/rte__mbuf_8h.html#a1215458932900b7cd5192326fa4a6902>(m);

/////////////////////////////////////////////////////////////////////

Now the problem here is the indirect mempool gets exhausted. As a result after 
few burst of packets the fragmentation fails due to -ENOMEM. I quite cannot 
understand why the PMD doesn't free and put back the mempool obj back to 
MEMPOOL1. Please find the log below for the above snippet which prints the 
available slots in direct (d) and indirect (in) mempools:

before frag mempool size d 2060457 in 2095988
after frag mempool size d 2060344 in 2095952
before frag mempool size d 2060361 in 2095945
after frag mempool size d 2060215 in 2095913
.
.
.
before frag mempool size d 2045013 in 0
after frag mempool size d 2045013 in 0
before frag mempool size d 2045013 in 0
after frag mempool size d 2045013 in 0
before frag mempool size d 2045013 in 0

I can see the direct mempool reduce and increase as packets ingress and 
drop/egress as expected. I can also confirm I receive the initial burst of 
fragmented packets equal to MEMPOOL1 size. Any inputs towards understanding the 
cause of the problem is much appreciated.

P.S: We had the same problem in dpdk17.11. We had to refractor the 
rte_ipv4_fragment_packet() to not use indirect chaining of frags instead just 
generate them.

Thanks & Regards,
Vishal Mohan


Tata Communications - Public


Tata Communications - Public