Performance tuning basic OS analysis

Top Command Analysis

Top command is used to show the Linux process

This command shows the summary information of the system and the list of process which are currently managed by the kernel

Top command we need to check two session summery session and task session

Summery session

System Time, Up time and user session

Load average

Tasks

CPU usage

Memory Usage


System Time, Up time and user session

top - 11:59:39 up 225 days, 22:31, 136 users,

System time: 11:59:39

Up time: up 225 days, 22hrs:31min

User session: 136 users connected.

Load average

Load average is the system load calculated over given period 1,5 and 15 minutes

Load average have 3 sessions

Load average: 4.43, 4.14, 4.03

Load average over last 1 minutes is 4.43

Load average over last 5 minutes is 4.14

Load average over last 15 minutes is 4.03

The high load average that system is overloaded many processes are waiting for CPU time

Tasks

Tasks session showing how many processes running total

Tasks: 1431 total, 5 running, 1426 sleeping, 0 stopped, 0 zombie

Total processes 1431

Running processes 5

Sleeping processes 1426

Stopped processes 0

Zombie processes 0

If zombie processes, we need to check otherwise it will consume more CPU and server process.

CPU usage

Cpu(s): 5.2%us, 0.3%sy, 0.0%ni, 94.4%id, 0.1%wa, 0.0%hi, 0.0%si, 0.0%st

us- User CPU time

sy- System CPU time

ni- User nice CPU time

Id- Idle CPU time

Wa- Wait IO CPU time

Hi- hardware interrupt

Si- software interrupt

St- steel time

Memory Usage

Memory usage we need to monitor 2 session physical memory and swap memory

Mem: 130083456k total, 126350812k used, 3732644k free, 2222124k buffers

Swap: 4194300k total, 355904k used, 3838396k free, 96284252k cached

Swap memory:

Swap space in Linux is used when the amount of physical memory (RAM) is full.

If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space.

While swap space can help machines with a small amount of RAM.

Buffers

Refers to data that is being written that memory cannot be reclaimed until the write is complete.

Cache

Refers to data that has been read -- it is kept around in case it needs to be read again, but can be immediately reclaimed since it can always be re-read from disk.

Task session


PID- Process Id.

User: Whish user started the process.

PR Or PRI: Process actual priority.

NI: Nice value.

VIRT: Virtual memory How much memory assigned to the process.

RES: Physical ram consumed by the process.

SHR: Shared memory.

%CPU: How much % using CPU for process

%MEM: How much % using memory for process

Vmstat Analysis

Virtual memory statistics report

Vmstat commands:

Vmstat -a list of active and inactive memory

Vmstat -s switch displays summary of various event counters and memory statistics.

vmstat with -d option display all disks statistics.

Process:

r- Number of processes in running state.

b- Number of processes in uninterruptible sleep state.

Memory

Swpd: The amount of virtual memory used.

Free: The amount of idle memory.

Buff: The amount of memory used as buffer.

Cache: The amount of memory used cache.

Swap

SI- The amount of memory swapped in from disk.

SO- The amount of memory swapped to disk

If si and so performing disk read and disk write operation. If it showing high value will get out of memory usage error.

IO

Bi- Blocks received from a block device.

BO- Blocks sent to a block device.

If BI and BO values is high database or server load high.

System:

In- Number of interrupts per second

Cs- Number of context switches per second

CPU

US: User process

SY: System process/OS process

Id: Idle time

Wa: Waiting for IO

 

Reference:

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