Bug 1687316

Summary: [dpdk] EAL control threads do not comply with cpu affinity
Product: Red Hat Enterprise Linux 8 Reporter: David Marchand <dmarchan>
Component: dpdkAssignee: David Marchand <dmarchan>
Status: CLOSED DUPLICATE QA Contact: Jean-Tsung Hsiao <jhsiao>
Severity: medium Docs Contact:
Priority: medium    
Version: 8.0CC: ailan, fhallal, ovs-qe, rkhan
Target Milestone: rc   
Target Release: 8.1   
Hardware: All   
OS: Unspecified   
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Clone Of:
: 1687319 1687320 (view as bug list) Environment:
Last Closed: 2019-06-27 11:28:15 UTC Type: Bug
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1682308    
Bug Blocks: 1687319, 1687320    

Description David Marchand 2019-03-11 09:03:02 UTC 
Description of problem:

The problem affects both Linux and FreeBSD implementations.
When a dpdk control thread is created (interrupt handler thread, multi process thread, vhost reconn thread, etc...), EAL constructs the cpu affinity of the newly created thread by looking at all availables cpu and remove the cpus from the startup corelist/coremask parameter.
The startup cpu affinity list is not taken into account which can have an impact on other performance critical processes running on the system.

How reproducible:
100%

Steps to Reproduce:
1. Start a dpdk application with a restricted cpu affinity list. Example:
taskset -c 0,1,2 testpmd -c 0x3 --no-pci --no-huge -m 512 -- -i --total-num-mbufs 2048


Actual results:
EAL started control threads out of the cpu affinity list:

$ grep -E '(Name|Cpus_allowed_list):' /proc/$(pidof testpmd)/task/*/status
/proc/87677/task/87677/status:Name:	testpmd
/proc/87677/task/87677/status:Cpus_allowed_list:	0
/proc/87677/task/87678/status:Name:	eal-intr-thread
/proc/87677/task/87678/status:Cpus_allowed_list:	2-27
/proc/87677/task/87679/status:Name:	rte_mp_handle
/proc/87677/task/87679/status:Cpus_allowed_list:	2-27
/proc/87677/task/87680/status:Name:	lcore-slave-1
/proc/87677/task/87680/status:Cpus_allowed_list:	1

Expected results:
Control threads should be kept in the initial cpu affinity list, not colliding with "datapath" threads specified via the coremask/corelist EAL parameters.


Additional info:

Bug reported upstream and fixed in commit:
https://git.dpdk.org/dpdk/commit/?id=c3568ea376700df061abcbeabc40ddaed7841e1a
Comment 1 David Marchand 2019-06-27 11:28:15 UTC 
Discussed with Timothy, let's handle this fix as part of the 18.11.2 rebase.

*** This bug has been marked as a duplicate of bug 1713702 ***