smp_affinity, taskset and isolcpus 指定CPU方法

• smp_affinity
  MV31是走USB介面，用lsusb查看，是用xhci_hcd

  $ lsusb
  Bus 004 Device 002: ID 1e2d:00b3 Gemalto M2M GmbH Cinterion PID 0x00B3 USB Mobile Broadband
  Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
  
  $ lsusb -t
  /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/8p, 20000M/x2
      |__ Port 2: Dev 2, If 0, Class=Communications, Driver=cdc_mbim, 5000M
      |__ Port 2: Dev 2, If 1, Class=CDC Data, Driver=cdc_mbim, 5000M
      |__ Port 2: Dev 2, If 2, Class=Vendor Specific Class, Driver=option, 5000M
      |__ Port 2: Dev 2, If 3, Class=Vendor Specific Class, Driver=, 5000M
      |__ Port 2: Dev 2, If 4, Class=Vendor Specific Class, Driver=option, 5000M
      |__ Port 2: Dev 2, If 5, Class=Vendor Specific Class, Driver=option, 5000M
  
  

  
  查下中斷表是否有xhci_hcd

  $ cat /proc/interrupts | grep -i xhci_hcd
   130:          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0  IR-PCI-MSI-0000:00:0d.0    0-edge      xhci_hcd
   132:          0        537          0          0          0          0          0          0          0          0          0          0          0      19774          0          0  IR-PCI-MSI-0000:00:14.0    0-edge      xhci_hcd
  

  
  中斷號碼132看起來在CPU13用得比較多(19774)
  用ping再度確認下
  CPU13變高到25209

  $ ping -I wwan0 8.8.8.8
  PING 8.8.8.8 (8.8.8.8) from 10.238.24.92 wwan0: 56(84) bytes of data.
  64 bytes from 8.8.8.8: icmp_seq=1 ttl=55 time=41.2 ms
  64 bytes from 8.8.8.8: icmp_seq=2 ttl=55 time=23.8 ms
  64 bytes from 8.8.8.8: icmp_seq=3 ttl=55 time=37.3 ms
  ^C
  --- 8.8.8.8 ping statistics ---
  3 packets transmitted, 3 received, 0% packet loss, time 2003ms
  rtt min/avg/max/mdev = 23.798/34.110/41.199/7.460 ms
  
  $ cat /proc/interrupts | grep -i xhci_hcd
   130:          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0  IR-PCI-MSI-0000:00:0d.0    0-edge      xhci_hcd
   132:          0        537          0          0          0          0          0          0          0          0          0          0          0      25209          0          0  IR-PCI-MSI-0000:00:14.0    0-edge      xhci_hcd
  

  
  系統用哪顆CPU來處理這個中斷

  $ cat /proc/irq/132/smp_affinity
  2020
  

  
  試著改變到CPU14和CPU15，並用PING再測試

  # echo "c000" > /proc/irq/132/smp_affinity
  
  # cat /proc/irq/132/smp_affinity
  c000
  
  $ cat /proc/interrupts | grep -i xhci_hcd
   130:          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0  IR-PCI-MSI-0000:00:0d.0    0-edge      xhci_hcd
   132:          0        537          0          0          0          0          0          0          0          0          0          0          0      35409       1373          0  IR-PCI-MSI-0000:00:14.0    0-edge      xhci_hcd
  

  
  queues

  $ cd /sys/class/net/wwan0/queues
  $ tree -L 1
  .
  ├── rx-0
  └── tx-0
  
  $ cat rx-0/rps_cpus
  0000  //這個值也能調整來提高效率
  

  
  
• taskset
  Install:

  $ sudo apt-get install util-linux
  

  
  查訊程式用哪顆CPU處理

  $ taskset -p PID
  $ taskset -p 6151
  pid 6151's current affinity mask: ffff
  

  
  指定程式用哪顆CPU處理

  $ taskset 8 /usr/local/bin/my_programer
  or
  $ taskset -p CPU_number PID
  
  $ taskset -p c000 6195
  pid 6195's current affinity mask: ffff
  pid 6195's new affinity mask: c000
  

  
  
  
• isolcpus尚末使用

ref:
1. [转]再转载一篇关于SMP IRQ affinity的好文章(包含RPS/RFS)
2. CPU Affinity taskset (cpuset)
3. 在 Linux 中以特定的 CPU 核心執行程式