Skip to main content

free command and options


Free command is frontend to /proc/meminfo file. It provide more human readable output to show you the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel:
$ free -m

vmstat command

===========================================

The vmstat, sar and iostat commands are the collection of package included in sysstat – the system monitoring tools. vmstat - Report virtual memory statistics. It reports information about processes, memory, paging, block IO, traps, disks and cpu activity. The  first report produced gives averages since the last reboot.  Additional reports give information on a sampling period of length delay.
Type the following command:
$vmstat
vmstat.png
FIELD DESCRIPTION FOR VM MODE
  Procs
      r: The number of runnable processes (running or waiting for run time).
      b: The number of processes in uninterruptible sleep.
  Memory
      swpd: the amount of virtual memory used.
      free: the amount of idle memory.
      buff: the amount of memory used as buffers.
      cache: the amount of memory used as cache.
      inact: the amount of inactive memory.  (-a option)
      active: the amount of active memory.  (-a option)
  Swap
      si: Amount of memory swapped in from disk (/s).
      so: Amount of memory swapped to disk (/s).
  IO
      bi: Blocks received from a block device (blocks/s).
      bo: Blocks sent to a block device (blocks/s).
  System
      in: The number of interrupts per second, including the clock.
      cs: The number of context switches per second.
Two important fields are free under memory and si, so under swap column
  1. Free – Amount of free/idle memory spaces.
  2. si – Swapped in every second from disk in Kilo Bytes.
  3. so – Swapped out every second to disk in Kilo Bytes.
OPTIONS
delay  The delay between updates in seconds.  If no delay is specified, only one report is printed with the average values since boot.
count  Number of updates.  In absence of count, when delay is defined, default is infinite.

Execute vmstat ‘X’ seconds and (‘N’ number of times)

$ vmstat 3 5

With this command, vmstat execute every 3 seconds and stop after executing 5 intervals.
Screenshot from 2015-07-22 10:30:41.png

-s, --stats Displays a table of various event counters and memory statistics.  This display does not repeat.
$ vmstat -s
Screenshot from 2015-07-22 10:32:12.png
-S, --unit character Switches outputs between 1000 (k), 1024 (K), 1000000 (m), or 1048576 (M) bytes.  Note this does not change the swap (si/so) or block
             (bi/bo) fields.
The vmstat displays in Megabytes with parameters -S and m. By default vmstat displays statistics in kilobytes.
$ vmstat -S m
Screenshot from 2015-07-22 10:36:29.png
    -d, --disk Report disk statistics
        $ vmstat -d
        Screenshot from 2015-07-22 10:42:07.png

Popular posts from this blog

How can you save resources when instantiaing driver?

I asked on my previous post about what was wrong in instantiating driver on set up method? And here is the solution video on my YouTube channel (After 5 years of gap I finally added new video tutorial :)) The solution described on video tutorial uses following set up - public class BaseClassOnDemandDriverSetup { private WebDriver driver ; @BeforeMethod public void setupTest () { // Any other set up goes here } @AfterMethod public void teardown () { if ( driver != null ) { driver .quit() ; } } public WebDriver getDriver () { if ( driver == null ) { WebDriverManager. chromedriver ().setup() ; driver = new ChromeDriver() ; } return driver ; } }

Using chrome console to test xPath and css selectors

Since the advent of selenium there have been many plugin to test xPath / css selectors but you don’t need any of them if you have chrome browser. Using Chrome console you can test both xPath and css selectors. Launch website to be tested in chrome browser and hit F-12 and you would see chrome console opened in lower pane of application - Hit escape key and console would open another pane to write element locators - And now you can start writing xPath or css selectors in chrome console and test them - The syntax for writing css id - $$(“ ”) And hit the enter key. If your expression is right then html snippet of the application element corresponding to the css selector would be displayed - If you mouse over the html snippet in chrome console then it would highlight the corresponding element in application - If you want to clean console of previously written element selectors then just hit ctrl+L keys and chrome console would be empty again. Pro

Using xPath to reach parent of an element

Well, I am big fan of css locator my self there are times when css locators don't fit requirement. One such requirement is when you want to navigate to parent element of an element and may be parent of parent and even more. Unfortunately css locators don't provide any mechanism to navigate to parent of an element. See this for more. Of late I came across a scenario when I wanted to click on a link depending upon the text in a text box. Herein parent of text box and parent of link were at the same location. More over there could have been many such combinations in application. Fortunately I just need to pick first such instance and Web Driver any way considers only first instance when multiple locators are found matching an element. Element in question is in following html - Here I need to click on highlighted anchor on the basis of input element (which is also highlighted in image) Herein first I need to reach div parent (class = 'left couponmainarea