[dpdk-dev] [Bug 50] Secondary process launch is unreliable

[bugzilla at dpdk.org]

https://dpdk.org/tracker/show_bug.cgi?id=50

            Bug ID: 50
           Summary: Secondary process launch is unreliable
           Product: DPDK
           Version: 18.05
          Hardware: All
                OS: All
            Status: CONFIRMED
          Severity: normal
          Priority: Normal
         Component: core
          Assignee: dev at dpdk.org
          Reporter: anatoly.burakov at intel.com
  Target Milestone: ---

Secondary process initialization was known to be unreliable before, with
numerous workarounds already being available and documented. However, DPDK
version 18.05 has introduced memory subsystem rework, which has made situation
worse due to much more memory being pre-reserved at initialization.

In addition, following investigation, it was revealed that DPDK secondary
processes ran with fork()/execv() method from within another DPDK application
(such as is the case with some DPDK unit tests) carry an additional risk of
initialization failures due to how pthread library appears to be working under
these conditions. Specifically, two IPC threads created by EAL will take up a
lot of address space (more than 10x of the usual amount), thereby interfering
with secondary process mappings and causing initialization failure. In this
case, disabling ASLR may actually make the situation worse, as
non-deterministic but sometimes lucky memory layout will be replaced by
deterministically wrong address mappings.

Things to try when affected by this issue:

* Using --base-virtaddr to relocate DPDK memory segments at initialization
* Not running DPDK applications using fork()/execv() method
* Enabling or disabling ASLR
* Recompiling the binary with different configuration
* Reducing the amount of preallocated memory (adjusting config options
CONFIG_RTE_MAX_MEM_MB_PER_TYPE and/or RTE_MAX_MEM_MB_PER_LIST)

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