[dpdk-users] Understanding the Proper way of using ip fragmentation

[Sungho Hong]

Hello DPDK experts,
I am having trouble applying ip fragmentation in multiple cores.
Really thankful if somebody can point out what I am doing wrong here.

*Purpose*
I am trying to apply ip fragmentation in multiple cores, and maximize the
throughput performance with messages that are bigger than MTU.

for each local & remote host (using 1 to 8 logical cores)
1 ~ 4 for transferring fragmented message
4 ~ 8 for receiving and assemble message

*Method of Throughput -testing *
Sending 4KB message from local and remote echos the message back to the
local.


*Problem *
If I try to allocate fragmentation table to each of the cores, I get a
segmentation error, and this happens no matter I shrink the size of the
fragmentation table.
The way I have tried to allocate the pools and frag-table are like this
below.

for each coreid, coreid < allocated cores; coreid++
     fragmentation_table[coreid] = rte_ip_frag_table_create(...);
     direct_pool[coreid] = rte_pktmbuf_pool_create(...);
     indirect_pool[coreid] rte_pktmbuf_pool_create(...);

So alternatively, I have allocated multiple fragmentation table for each
lcores but let the direct and indirect pools be shared together.

for each coreid, coreid < allocated cores; coreid++
     fragmentation_table[coreid] = rte_ip_frag_table_create(...);

direct_pool = rte_pktmbuf_pool_create(...);
indirect_pool = rte_pktmbuf_pool_create(...);

*Situation*
Now when I send messages using multiple cores from local to remote host,
the remote host only successfully receive the message when I send the
message adding a delay such as ( adding sleep(1); for each message send. )
I was able to receive the message from local to remote. But, cannot receive
any data when I try to send them without any delay.


Personally, I suspect that I should allocate direct pool and indirect pool
for each logical cores, and I think that is the main issue. Since I was
only able to successfully use the frag-table using only one logical core, I
suspect that I am not using the fragmentation table correctly in multiple
cores.


I really want to hear from the DPDK experts about this issue I am facing,
and will be really grateful for any advice on this...