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From: bugzilla@dpdk.org
To: dev@dpdk.org
Subject: [Bug 1137] CPU affinity set incorrectly when lcore_id 0 is not the
master-lcore
Date: Wed, 30 Nov 2022 18:41:16 +0000
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X-Bugzilla-Product: DPDK
X-Bugzilla-Component: core
X-Bugzilla-Version: 22.11
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X-Bugzilla-Who: ltroup@cisco.com
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https://bugs.dpdk.org/show_bug.cgi?id=3D1137
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: ltroup@cisco.com
Target Milestone: ---
Created attachment 233
--> https://bugs.dpdk.org/attachment.cgi?id=3D233&action=3Dedit
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 cp=
uset
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 se=
t to
0.
This means that internally, the lcore_id for the control-thread is set to 0=
-
and=20
in particular, the call to thread_update_affinity() overwrites the cpuset f=
or
lcore_id=3D0 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 thr=
ead
- so that the slave thread associated with lcore_id, which should be runnin=
g 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 ass=
ign
an lcore-id, then passes this to __rte_thread_init(). I have tested a fix f=
or
this locally to confirm.
--=20
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