https://bugs.dpdk.org/show_bug.cgi?id=1137
Bug ID: 1137
Summary: CPU affinity set incorrectly when lcore_id 0 is not
the master-lcore
Product: DPDK
Version: 22.11
Hardware: All
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: core
Assignee: dev@dpdk.org
Reporter: ltr...@cisco.com
Target Milestone: ---
Created attachment 233
--> https://bugs.dpdk.org/attachment.cgi?id=233&action=edit
Logs showing incorrect CPU set assignment
When a range of CPUs are used (e.g. 0-3), and the master-lcore is set to
non-zero, the CPU affinity for lcore-id 0 is set incorrectly, due to its cpuset
being overwritten by the control-thread creation.
CPU arguments passed are '-c f --master-lcore 3', to indicate that CPUs 0-3
should be used, with the master on CPU 3. In particular, DPDK itself is
initialized from CPU 3.
When the control threads (eal-intr-thread, rte_mp_handle) are created, they are
initialized from CPU3 - so inherit the cpuset containing just this CPU. When
calling __rte_thread_init(), ctrl_thread_init() passes the result of
rte_lcore_id() - but this is not yet initialized for this thread - so is set to
0.
This means that internally, the lcore_id for the control-thread is set to 0 -
and
in particular, the call to thread_update_affinity() overwrites the cpuset for
lcore_id=0 with the cpuset of CPU3:
memmove(&lcore_config[lcore_id].cpuset, cpusetp,
sizeof(rte_cpuset_t));
This all occurs before the main __rte_thread_init() call for each Slave thread
- so that the slave thread associated with lcore_id, which should be running on
CPU0, instead has its affinity incorrectly set to CPU3.
RTE logs are attached showing this behavior (and including some additional logs
added locally to print the lcore-id and cpusets being passed).
The fix for this should be to make ctrl_thread_init() more similar to
rte_thread_register(), so that it calls eal_lcore_non_eal_allocate() to assign
an lcore-id, then passes this to __rte_thread_init(). I have tested a fix for
this locally to confirm.
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