Linux tuning (memory, CPU)

I. Introduction to concepts

• system call: system calls
• time slice: cpu time slice
• O (1): Linux system process scheduler
• page frame: Page
• RSS: permanent memory set can not be a page of data
• MMU: memory management unit mapping table maintains a linear address space and physical address space
• TLB: the conversion buffer
• huge page: large page
• NUMA: Non-uniform memory access, multiple-CPU, each CPU has its own memory segments, each segment is called a node, the process is recommended do CPU affinity binding

Two, CPU memory tuning

• Affinity tune with the CPU process

# taskset -p mask pid
# taskset mask -- program
# taskset -c 0,,2-7 -- myprogram

# taskset -p -c 1 17947  #将pid为17947的进程绑定至第2颗CPU上，重启失效

• View processes that are currently running on the CPU which pieces

# ps axo psr,pid,cmd

• cpu interrupt statistics

# cat /proc/interrupts

• numactl: Policy Management for MUMA
• Adjust process priority: nice, renice
• Isolation CPU, the CPU will not be quarantined interrupt processing

# vim /etc/grub.conf
    kernel ...... lsolcpus=1,2,3...

• Scheduling categories:

SCHED_FIFO [0-99]
    chrt -f [1-99] /path/to/program arguments
SCHED_RR
    chrt -f [1-99] /path/to/program arguments
SCHED_NORMAL [100-139]
    nice，renice

• 0 - 139

1-99：实时优先级
100-139：动态优先级

• Performance monitoring tools

htop
dstat
glances
sysdig
sar -P ALL 1 2
vmstat 1 5
iostat -c 1

• Configuring large page

vm.nr_hugepages = 10

• The current system maximum number of files open

fs.file-max = 8192

• So the current asynchronous io allow the maximum number of system events

fs.aio-max-nr = 65535

• OOM adjustable parameters

vm.panic_on_oom = 0
/proc/pid/oom_adj  [-16-15] #数字越高，被杀死的值越大，如果是-17则这个进程是无懈可击的

Third, memory summary

nr_hugepages
swapiness
overcommit_memory