When adding a small form-factor pluggable (SFP) to the uplink module of EX4300, the CPU usage of pfex_junos process increases. Whenever an SFP is added, software linkscan is enabled by default which causes the CPU utilization to go up.
root> show system processes extensive no-forwarding last pid: 29536; load averages: 0.68, 0.39, 0.36 up 207+01:08:29 03:41:02 147 processes: 4 running, 120 sleeping, 2 zombie, 21 waiting Mem: 698M Active, 104M Inact, 151M Wired, 381M Cache, 112M Buf, 1531M Free Swap: PID USERNAME THR PRI NICE SIZE RES STATE TIME WCPU COMMAND 10 root 1 171 52 0K 16K RUN 2902.2 55.22% idle 1159 root 2 44 -52 560M 206M umtx 1833.1 29.69% pfex_junos root> show chassis hardware detail no-forwarding Hardware inventory: Item Version Part number Serial number Description Chassis TW3716170123 Virtual Chassis Routing Engine 0 REV 03 650-064274 TW3716170123 EX4300-32F Routing Engine 1 REV 19 650-044931 PE3716150608 EX4300-48T FPC 0 REV 03 650-064274 TW3716170123 EX4300-32F CPU BUILTIN BUILTIN FPC CPU PIC 0 REV 03 BUILTIN BUILTIN 32x 1G SFP, 4x 1G/10G SFP/SFP+ Xcvr 32 REV 01 740-021309 G3G2002975 SFP+-10G-LR Xcvr 33 REV 01 740-021309 G2U2007763 SFP+-10G-LR Xcvr 34 REV 01 740-021309 G3G2003132 SFP+-10G-LR Xcvr 35 REV 01 740-021309 G3G2003088 SFP+-10G-LR
last pid: 29536; load averages: 0.68, 0.39, 0.36 up 207+01:08:29 03:41:02 147 processes: 4 running, 120 sleeping, 2 zombie, 21 waiting Mem: 698M Active, 104M Inact, 151M Wired, 381M Cache, 112M Buf, 1531M Free Swap: PID USERNAME THR PRI NICE SIZE RES STATE TIME WCPU COMMAND 10 root 1 171 52 0K 16K RUN 2902.2 55.22% idle 1159 root 2 44 -52 560M 206M umtx 1833.1 29.69% pfex_junos root> show chassis hardware detail no-forwarding Hardware inventory: Item Version Part number Serial number Description Chassis TW3716170123 Virtual Chassis Routing Engine 0 REV 03 650-064274 TW3716170123 EX4300-32F Routing Engine 1 REV 19 650-044931 PE3716150608 EX4300-48T FPC 0 REV 03 650-064274 TW3716170123 EX4300-32F CPU BUILTIN BUILTIN FPC CPU PIC 0 REV 03 BUILTIN BUILTIN 32x 1G SFP, 4x 1G/10G SFP/SFP+ Xcvr 32 REV 01 740-021309 G3G2002975 SFP+-10G-LR Xcvr 33 REV 01 740-021309 G2U2007763 SFP+-10G-LR Xcvr 34 REV 01 740-021309 G3G2003132 SFP+-10G-LR Xcvr 35 REV 01 740-021309 G3G2003088 SFP+-10G-LR
This is a product limitation, because software linkscan is enabled by default, which causes the CPU utilization to go up. There is no way to disable it. EX4300 uses a combination of hardware and software linkscan.
BCM.0> link LINKscan: Linkscan enabled LINKscan: Software polling interval: 25000 usec LINKscan: Software Port BitMap 0x0000000000000000000000000000000000000000000000000000bc0000000000: xe0-xe3,hg LINKscan: Hardware Port BitMap 0x000000000000000000000000000000000000000000000000000000000003fffe: ge0-ge16 LINKscan: Disabled Port BitMap 0x00000000000000000000000000000000000000000000000000ff403ffffc0000: ge17-ge36,xe4-xe12
With 17 1G SFPs in the front panel ports on an unloaded system, the pfex CPU utilization hovers at around .5%. On plugging in an optic to the uplink or the rear 40G ports, thereby starting software linkscan, the utilization goes up to about 11%. Every additional optic plugged in increases the utilization by about 1%.
2018-10-29: Minor edit. Non-technical.